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* Merge branch 'akpm' (patches from Andrew)Linus Torvalds2015-04-151-74/+215
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Merge first patchbomb from Andrew Morton: - arch/sh updates - ocfs2 updates - kernel/watchdog feature - about half of mm/ * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (122 commits) Documentation: update arch list in the 'memtest' entry Kconfig: memtest: update number of test patterns up to 17 arm: add support for memtest arm64: add support for memtest memtest: use phys_addr_t for physical addresses mm: move memtest under mm mm, hugetlb: abort __get_user_pages if current has been oom killed mm, mempool: do not allow atomic resizing memcg: print cgroup information when system panics due to panic_on_oom mm: numa: remove migrate_ratelimited mm: fold arch_randomize_brk into ARCH_HAS_ELF_RANDOMIZE mm: split ET_DYN ASLR from mmap ASLR s390: redefine randomize_et_dyn for ELF_ET_DYN_BASE mm: expose arch_mmap_rnd when available s390: standardize mmap_rnd() usage powerpc: standardize mmap_rnd() usage mips: extract logic for mmap_rnd() arm64: standardize mmap_rnd() usage x86: standardize mmap_rnd() usage arm: factor out mmap ASLR into mmap_rnd ...
| * watchdog: introduce the hardlockup_detector_disable() functionUlrich Obergfell2015-04-151-19/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Have kvm_guest_init() use hardlockup_detector_disable() instead of watchdog_enable_hardlockup_detector(false). Remove the watchdog_hardlockup_detector_is_enabled() and the watchdog_enable_hardlockup_detector() function which are no longer needed. Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * watchdog: clean up some function names and argumentsUlrich Obergfell2015-04-151-8/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Rename the update_timers*() functions to update_watchdog*(). Remove the boolean argument from watchdog_enable_all_cpus() because update_watchdog_all_cpus() is now a generic function to change the run state of the lockup detectors and to have the lockup detectors use a new sample period. Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * watchdog: enable the new user interface of the watchdog mechanismUlrich Obergfell2015-04-151-65/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With the current user interface of the watchdog mechanism it is only possible to disable or enable both lockup detectors at the same time. This series introduces new kernel parameters and changes the semantics of some existing kernel parameters, so that the hard lockup detector and the soft lockup detector can be disabled or enabled individually. With this series applied, the user interface is as follows. - parameters in /proc/sys/kernel . soft_watchdog This is a new parameter to control and examine the run state of the soft lockup detector. . nmi_watchdog The semantics of this parameter have changed. It can now be used to control and examine the run state of the hard lockup detector. . watchdog This parameter is still available to control the run state of both lockup detectors at the same time. If this parameter is examined, it shows the logical OR of soft_watchdog and nmi_watchdog. . watchdog_thresh The semantics of this parameter are not affected by the patch. - kernel command line parameters . nosoftlockup The semantics of this parameter have changed. It can now be used to disable the soft lockup detector at boot time. . nmi_watchdog=0 or nmi_watchdog=1 Disable or enable the hard lockup detector at boot time. The patch introduces '=1' as a new option. . nowatchdog The semantics of this parameter are not affected by the patch. It is still available to disable both lockup detectors at boot time. Also, remove the proc_dowatchdog() function which is no longer needed. [dzickus@redhat.com: wrote changelog] [dzickus@redhat.com: update documentation for kernel params and sysctl] Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * watchdog: implement error handling for failure to set up hardware perf eventsUlrich Obergfell2015-04-151-0/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | If watchdog_nmi_enable() fails to set up the hardware perf event of one CPU, the entire hard lockup detector is deemed unreliable. Hence, disable the hard lockup detector and shut down the hardware perf events on all CPUs. [dzickus@redhat.com: update comments to explain some code] Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * watchdog: introduce separate handlers for parameters in /proc/sys/kernelUlrich Obergfell2015-04-151-0/+59
| | | | | | | | | | | | | | | | | | | | | | | | Separate handlers for each watchdog parameter in /proc/sys/kernel replace the proc_dowatchdog() function. Three of those handlers merely call proc_watchdog_common() with one different argument. Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * watchdog: introduce proc_watchdog_common()Ulrich Obergfell2015-04-151-0/+65
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Three of four handlers for the watchdog parameters in /proc/sys/kernel essentially have to do the same thing. if the parameter is being read { return the state of the corresponding bit(s) in 'watchdog_enabled' } else { set/clear the state of the corresponding bit(s) in 'watchdog_enabled' update the run state of the lockup detector(s) } Hence, introduce a common function that can be called by those handlers. The callers pass a 'bit mask' to this function to indicate which bit(s) should be set/cleared in 'watchdog_enabled'. This function handles an uncommon race with watchdog_nmi_enable() where a concurrent update of 'watchdog_enabled' is possible. We use 'cmpxchg' to detect the concurrency. [This avoids introducing a new spinlock or a mutex to synchronize updates of 'watchdog_enabled'. Using the same lock or mutex in watchdog thread context and in system call context needs to be considered carefully because it can make the code prone to deadlock situations in connection with parking/unparking the watchdog threads.] Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * watchdog: move definition of 'watchdog_proc_mutex' outside of proc_dowatchdog()Ulrich Obergfell2015-04-151-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | This series removes proc_dowatchdog(). Since multiple new functions need the 'watchdog_proc_mutex' to serialize access to the watchdog parameters in /proc/sys/kernel, move the mutex outside of any function. Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * watchdog: introduce the proc_watchdog_update() functionUlrich Obergfell2015-04-151-0/+23
| | | | | | | | | | | | | | | | | | | | | | | | | | This series introduces a separate handler for each watchdog parameter in /proc/sys/kernel. The separate handlers need a common function that they can call to update the run state of the lockup detectors, or to have the lockup detectors use a new sample period. Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * watchdog: new definitions and variables, initializationUlrich Obergfell2015-04-151-1/+26
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The hardlockup and softockup had always been tied together. Due to the request of KVM folks, they had a need to have one enabled but not the other. Internally rework the code to split things apart more cleanly. There is a bunch of churn here, but the end result should be code that should be easier to maintain and fix without knowing the internals of what is going on. This patch (of 9): Introduce new definitions and variables to separate the user interface in /proc/sys/kernel from the internal run state of the lockup detectors. The internal run state is represented by two bits in a new variable that is named 'watchdog_enabled'. This helps simplify the code, for example: - In order to check if any of the two lockup detectors is enabled, it is sufficient to check if 'watchdog_enabled' is not zero. - In order to enable/disable one or both lockup detectors, it is sufficient to set/clear one or both bits in 'watchdog_enabled'. - Concurrent updates of 'watchdog_enabled' need not be synchronized via a spinlock or a mutex. Updates can either be atomic or concurrency can be detected by using 'cmpxchg'. Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | watchdog: Add watchdog enable/disable all functionsStephane Eranian2015-04-021-0/+28
|/ | | | | | | | | | | | | | | | | | | | This patch adds two new functions to enable/disable the watchdog across all CPUs. This will be used by the HT PMU bug workaround code to disable/enable the NMI watchdog across quirk enablement. Signed-off-by: Stephane Eranian <eranian@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: bp@alien8.de Cc: jolsa@redhat.com Cc: kan.liang@intel.com Cc: maria.n.dimakopoulou@gmail.com Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1416251225-17721-12-git-send-email-eranian@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* kernel/sched/clock.c: add another clock for use with the soft lockup watchdogCyril Bur2015-02-131-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the hypervisor pauses a virtualised kernel the kernel will observe a jump in timebase, this can cause spurious messages from the softlockup detector. Whilst these messages are harmless, they are accompanied with a stack trace which causes undue concern and more problematically the stack trace in the guest has nothing to do with the observed problem and can only be misleading. Futhermore, on POWER8 this is completely avoidable with the introduction of the Virtual Time Base (VTB) register. This patch (of 2): This permits the use of arch specific clocks for which virtualised kernels can use their notion of 'running' time, not the elpased wall time which will include host execution time. Signed-off-by: Cyril Bur <cyrilbur@gmail.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Andrew Jones <drjones@redhat.com> Acked-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: chai wen <chaiw.fnst@cn.fujitsu.com> Cc: Fabian Frederick <fabf@skynet.be> Cc: Aaron Tomlin <atomlin@redhat.com> Cc: Ben Zhang <benzh@chromium.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge branch 'for-3.18-consistent-ops' of ↵Linus Torvalds2014-10-151-6/+6
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu Pull percpu consistent-ops changes from Tejun Heo: "Way back, before the current percpu allocator was implemented, static and dynamic percpu memory areas were allocated and handled separately and had their own accessors. The distinction has been gone for many years now; however, the now duplicate two sets of accessors remained with the pointer based ones - this_cpu_*() - evolving various other operations over time. During the process, we also accumulated other inconsistent operations. This pull request contains Christoph's patches to clean up the duplicate accessor situation. __get_cpu_var() uses are replaced with with this_cpu_ptr() and __this_cpu_ptr() with raw_cpu_ptr(). Unfortunately, the former sometimes is tricky thanks to C being a bit messy with the distinction between lvalues and pointers, which led to a rather ugly solution for cpumask_var_t involving the introduction of this_cpu_cpumask_var_ptr(). This converts most of the uses but not all. Christoph will follow up with the remaining conversions in this merge window and hopefully remove the obsolete accessors" * 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (38 commits) irqchip: Properly fetch the per cpu offset percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t -fix ia64: sn_nodepda cannot be assigned to after this_cpu conversion. Use __this_cpu_write. percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t Revert "powerpc: Replace __get_cpu_var uses" percpu: Remove __this_cpu_ptr clocksource: Replace __this_cpu_ptr with raw_cpu_ptr sparc: Replace __get_cpu_var uses avr32: Replace __get_cpu_var with __this_cpu_write blackfin: Replace __get_cpu_var uses tile: Use this_cpu_ptr() for hardware counters tile: Replace __get_cpu_var uses powerpc: Replace __get_cpu_var uses alpha: Replace __get_cpu_var ia64: Replace __get_cpu_var uses s390: cio driver &__get_cpu_var replacements s390: Replace __get_cpu_var uses mips: Replace __get_cpu_var uses MIPS: Replace __get_cpu_var uses in FPU emulator. arm: Replace __this_cpu_ptr with raw_cpu_ptr ...
| * watchdog: Replace __raw_get_cpu_var usesChristoph Lameter2014-08-261-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | Most of these are the uses of &__raw_get_cpu_var for address calculation. touch_softlockup_watchdog_sync() uses __raw_get_cpu_var to write to per cpu variables. Use __this_cpu_write instead. Cc: Wim Van Sebroeck <wim@iguana.be> Cc: linux-watchdog@vger.kernel.org Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | kernel/watchdog.c: control hard lockup detection defaultUlrich Obergfell2014-10-141-2/+48
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In some cases we don't want hard lockup detection enabled by default. An example is when running as a guest. Introduce watchdog_enable_hardlockup_detector(bool) allowing those cases to disable hard lockup detection. This must be executed early by the boot processor from e.g. smp_prepare_boot_cpu, in order to allow kernel command line arguments to override it, as well as to avoid hard lockup detection being enabled before we've had a chance to indicate that it's unwanted. In summary, initial boot: default=enabled smp_prepare_boot_cpu watchdog_enable_hardlockup_detector(false): default=disabled cmdline has 'nmi_watchdog=1': default=enabled The running kernel still has the ability to enable/disable at any time with /proc/sys/kernel/nmi_watchdog us usual. However even when the default has been overridden /proc/sys/kernel/nmi_watchdog will initially show '1'. To truly turn it on one must disable/enable it, i.e. echo 0 > /proc/sys/kernel/nmi_watchdog echo 1 > /proc/sys/kernel/nmi_watchdog This patch will be immediately useful for KVM with the next patch of this series. Other hypervisor guest types may find it useful as well. [akpm@linux-foundation.org: fix build] [dzickus@redhat.com: fix compile issues on sparc] Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Andrew Jones <drjones@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | Merge branch 'perf-watchdog-for-linus' of ↵Linus Torvalds2014-10-131-6/+4
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull watchdog fixes from Ingo Molnar: "Two small watchdog subsystem fixes" * 'perf-watchdog-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: watchdog: Fix print-once on enable watchdog: Remove unnecessary header files
| * | watchdog: Fix print-once on enableUlrich Obergfell2014-08-181-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch avoids printing the message 'enabled on all CPUs, ...' multiple times. For example, the issue can occur in the following scenario: 1) watchdog_nmi_enable() fails to enable PMU counters and sets cpu0_err. 2) 'echo [0|1] > /proc/sys/kernel/nmi_watchdog' is executed to disable and re-enable the watchdog mechanism 'on the fly'. 3) If watchdog_nmi_enable() succeeds to enable PMU counters, each CPU will print the message because step1 left behind a non-zero cpu0_err. if (!IS_ERR(event)) { if (cpu == 0 || cpu0_err) pr_info("enabled on all CPUs, ...") The patch avoids this by clearing cpu0_err in watchdog_nmi_disable(). Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Andrew Jones <drjones@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: pbonzini@redhat.com Link: http://lkml.kernel.org/r/1407768567-171794-4-git-send-email-dzickus@redhat.com [ Applied small cleanups. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | watchdog: Remove unnecessary header fileschai wen2014-08-181-5/+0
| | | | | | | | | | | | | | | | | | | | | | | | Signed-off-by: chai wen <chaiw.fnst@cn.fujitsu.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: pbonzini@redhat.com Link: http://lkml.kernel.org/r/1407768567-171794-2-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | | softlockup: make detector be aware of task switch of processes hogging cpuchai wen2014-10-101-1/+17
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For now, soft lockup detector warns once for each case of process softlockup. But the thread 'watchdog/n' may not always get the cpu at the time slot between the task switch of two processes hogging that cpu to reset soft_watchdog_warn. An example would be two processes hogging the cpu. Process A causes the softlockup warning and is killed manually by a user. Process B immediately becomes the new process hogging the cpu preventing the softlockup code from resetting the soft_watchdog_warn variable. This case is a false negative of "warn only once for a process", as there may be a different process that is going to hog the cpu. Resolve this by saving/checking the task pointer of the hogging process and use that to reset soft_watchdog_warn too. [dzickus@redhat.com: update comment] Signed-off-by: chai wen <chaiw.fnst@cn.fujitsu.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | panic: add TAINT_SOFTLOCKUPJosh Hunt2014-08-091-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | This taint flag will be set if the system has ever entered a softlockup state. Similar to TAINT_WARN it is useful to know whether or not the system has been in a softlockup state when debugging. [akpm@linux-foundation.org: apply the taint before calling panic()] Signed-off-by: Josh Hunt <johunt@akamai.com> Cc: Jason Baron <jbaron@akamai.com> Cc: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | kernel/watchdog.c: convert printk/pr_warning to pr_foo()Fabian Frederick2014-08-071-4/+6
|/ | | | | | | | | Replace some obsolete functions. Signed-off-by: Fabian Frederick <fabf@skynet.be> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* kernel/watchdog.c: print traces for all cpus on lockup detectionAaron Tomlin2014-06-241-0/+39
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A 'softlockup' is defined as a bug that causes the kernel to loop in kernel mode for more than a predefined period to time, without giving other tasks a chance to run. Currently, upon detection of this condition by the per-cpu watchdog task, debug information (including a stack trace) is sent to the system log. On some occasions, we have observed that the "victim" rather than the actual "culprit" (i.e. the owner/holder of the contended resource) is reported to the user. Often this information has proven to be insufficient to assist debugging efforts. To avoid loss of useful debug information, for architectures which support NMI, this patch makes it possible to improve soft lockup reporting. This is accomplished by issuing an NMI to each cpu to obtain a stack trace. If NMI is not supported we just revert back to the old method. A sysctl and boot-time parameter is available to toggle this feature. [dzickus@redhat.com: add CONFIG_SMP in certain areas] [akpm@linux-foundation.org: additional CONFIG_SMP=n optimisations] [mq@suse.cz: fix warning] Signed-off-by: Aaron Tomlin <atomlin@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Mateusz Guzik <mguzik@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Jan Moskyto Matejka <mq@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* kernel/watchdog.c: remove preemption restrictions when restarting lockup ↵Don Zickus2014-06-241-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | detector Peter Wu noticed the following splat on his machine when updating /proc/sys/kernel/watchdog_thresh: BUG: sleeping function called from invalid context at mm/slub.c:965 in_atomic(): 1, irqs_disabled(): 0, pid: 1, name: init 3 locks held by init/1: #0: (sb_writers#3){.+.+.+}, at: [<ffffffff8117b663>] vfs_write+0x143/0x180 #1: (watchdog_proc_mutex){+.+.+.}, at: [<ffffffff810e02d3>] proc_dowatchdog+0x33/0x110 #2: (cpu_hotplug.lock){.+.+.+}, at: [<ffffffff810589c2>] get_online_cpus+0x32/0x80 Preemption disabled at:[<ffffffff810e0384>] proc_dowatchdog+0xe4/0x110 CPU: 0 PID: 1 Comm: init Not tainted 3.16.0-rc1-testing #34 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: dump_stack+0x4e/0x7a __might_sleep+0x11d/0x190 kmem_cache_alloc_trace+0x4e/0x1e0 perf_event_alloc+0x55/0x440 perf_event_create_kernel_counter+0x26/0xe0 watchdog_nmi_enable+0x75/0x140 update_timers_all_cpus+0x53/0xa0 proc_dowatchdog+0xe4/0x110 proc_sys_call_handler+0xb3/0xc0 proc_sys_write+0x14/0x20 vfs_write+0xad/0x180 SyS_write+0x49/0xb0 system_call_fastpath+0x16/0x1b NMI watchdog: disabled (cpu0): hardware events not enabled What happened is after updating the watchdog_thresh, the lockup detector is restarted to utilize the new value. Part of this process involved disabling preemption. Once preemption was disabled, perf tried to allocate a new event (as part of the restart). This caused the above BUG_ON as you can't sleep with preemption disabled. The preemption restriction seemed agressive as we are not doing anything on that particular cpu, but with all the online cpus (which are protected by the get_online_cpus lock). Remove the restriction and the BUG_ON goes away. Signed-off-by: Don Zickus <dzickus@redhat.com> Acked-by: Michal Hocko <mhocko@suse.cz> Reported-by: Peter Wu <peter@lekensteyn.nl> Tested-by: Peter Wu <peter@lekensteyn.nl> Acked-by: David Rientjes <rientjes@google.com> Cc: <stable@vger.kernel.org> [3.13+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* kernel/watchdog.c:touch_softlockup_watchdog(): use raw_cpu_write()Andrew Morton2014-04-191-1/+5
| | | | | | | | | | | | | | | | | | | | | | | | Fix: BUG: using __this_cpu_write() in preemptible [00000000] code: systemd-udevd/497 caller is __this_cpu_preempt_check+0x13/0x20 CPU: 3 PID: 497 Comm: systemd-udevd Tainted: G W 3.15.0-rc1 #9 Hardware name: Hewlett-Packard HP EliteBook 8470p/179B, BIOS 68ICF Ver. F.02 04/27/2012 Call Trace: check_preemption_disabled+0xe1/0xf0 __this_cpu_preempt_check+0x13/0x20 touch_nmi_watchdog+0x28/0x40 Reported-by: Luis Henriques <luis.henriques@canonical.com> Tested-by: Luis Henriques <luis.henriques@canonical.com> Cc: Eric Piel <eric.piel@tremplin-utc.net> Cc: Robert Moore <robert.moore@intel.com> Cc: Lv Zheng <lv.zheng@intel.com> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Christoph Lameter <cl@linux.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* kernel/watchdog.c: touch_nmi_watchdog should only touch local cpu not every oneBen Zhang2014-04-041-8/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | I ran into a scenario where while one cpu was stuck and should have panic'd because of the NMI watchdog, it didn't. The reason was another cpu was spewing stack dumps on to the console. Upon investigation, I noticed that when writing to the console and also when dumping the stack, the watchdog is touched. This causes all the cpus to reset their NMI watchdog flags and the 'stuck' cpu just spins forever. This change causes the semantics of touch_nmi_watchdog to be changed slightly. Previously, I accidentally changed the semantics and we noticed there was a codepath in which touch_nmi_watchdog could be touched from a preemtible area. That caused a BUG() to happen when CONFIG_DEBUG_PREEMPT was enabled. I believe it was the acpi code. My attempt here re-introduces the change to have the touch_nmi_watchdog() code only touch the local cpu instead of all of the cpus. But instead of using __get_cpu_var(), I use the __raw_get_cpu_var() version. This avoids the preemption problem. However my reasoning wasn't because I was trying to be lazy. Instead I rationalized it as, well if preemption is enabled then interrupts should be enabled to and the NMI watchdog will have no reason to trigger. So it won't matter if the wrong cpu is touched because the percpu interrupt counters the NMI watchdog uses should still be incrementing. Don said: : I'm ok with this patch, though it does alter the behaviour of how : touch_nmi_watchdog works. For the most part I don't think most callers : need to touch all of the watchdogs (on each cpu). Perhaps a corner case : will pop up (the scheduler?? to mimic touch_all_softlockup_watchdogs() ). : : But this does address an issue where if a system is locked up and one cpu : is spewing out useful debug messages (or error messages), the hard lockup : will fail to go off. We have seen this on RHEL also. Signed-off-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Ben Zhang <benzh@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* watchdog: Simplify a little the IPI callFrederic Weisbecker2014-02-241-2/+1
| | | | | | | | | | | | | | | | | | | | | | In order to remotely restart the watchdog hrtimer, update_timers() allocates a csd on the stack and pass it to __smp_call_function_single(). There is no partcular need, however, for a specific csd here. Lets simplify that a little by calling smp_call_function_single() which can already take care of the csd allocation by itself. Acked-by: Don Zickus <dzickus@redhat.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@fb.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* watchdog: update watchdog_thresh properlyMichal Hocko2013-09-251-3/+50
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | watchdog_tresh controls how often nmi perf event counter checks per-cpu hrtimer_interrupts counter and blows up if the counter hasn't changed since the last check. The counter is updated by per-cpu watchdog_hrtimer hrtimer which is scheduled with 2/5 watchdog_thresh period which guarantees that hrtimer is scheduled 2 times per the main period. Both hrtimer and perf event are started together when the watchdog is enabled. So far so good. But... But what happens when watchdog_thresh is updated from sysctl handler? proc_dowatchdog will set a new sampling period and hrtimer callback (watchdog_timer_fn) will use the new value in the next round. The problem, however, is that nobody tells the perf event that the sampling period has changed so it is ticking with the period configured when it has been set up. This might result in an ear ripping dissonance between perf and hrtimer parts if the watchdog_thresh is increased. And even worse it might lead to KABOOM if the watchdog is configured to panic on such a spurious lockup. This patch fixes the issue by updating both nmi perf even counter and hrtimers if the threshold value has changed. The nmi one is disabled and then reinitialized from scratch. This has an unpleasant side effect that the allocation of the new event might fail theoretically so the hard lockup detector would be disabled for such cpus. On the other hand such a memory allocation failure is very unlikely because the original event is deallocated right before. It would be much nicer if we just changed perf event period but there doesn't seem to be any API to do that right now. It is also unfortunate that perf_event_alloc uses GFP_KERNEL allocation unconditionally so we cannot use on_each_cpu() and do the same thing from the per-cpu context. The update from the current CPU should be safe because perf_event_disable removes the event atomically before it clears the per-cpu watchdog_ev so it cannot change anything under running handler feet. The hrtimer is simply restarted (thanks to Don Zickus who has pointed this out) if it is queued because we cannot rely it will fire&adopt to the new sampling period before a new nmi event triggers (when the treshold is decreased). [akpm@linux-foundation.org: the UP version of __smp_call_function_single ended up in the wrong place] Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: Don Zickus <dzickus@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Fabio Estevam <festevam@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* watchdog: update watchdog attributes atomicallyMichal Hocko2013-09-251-2/+5
| | | | | | | | | | | | | | | | | | proc_dowatchdog doesn't synchronize multiple callers which might lead to confusion when two parallel callers might confuse watchdog_enable_all_cpus resp watchdog_disable_all_cpus (eg watchdog gets enabled even if watchdog_thresh was set to 0 already). This patch adds a local mutex which synchronizes callers to the sysctl handler. Signed-off-by: Michal Hocko <mhocko@suse.cz> Cc: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: Don Zickus <dzickus@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* watchdog: Make it work under full dynticksFrederic Weisbecker2013-07-301-8/+0
| | | | | | | | | | | | | | | | | | | | | | | | A perf event can be used without forcing the tick to stay alive if it doesn't use a frequency but a sample period and if it doesn't throttle (raise storm of events). Since the lockup detector neither use a perf event frequency nor should ever throttle due to its high period, it can now run concurrently with the full dynticks feature. So remove the hack that disabled the watchdog. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com> Cc: Don Zickus <dzickus@redhat.com> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Anish Singh <anish198519851985@gmail.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1374539466-4799-9-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog: Boot-disable by default on full dynticksFrederic Weisbecker2013-06-201-0/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the watchdog runs, it prevents the full dynticks CPUs from stopping their tick because the hard lockup detector uses perf events internally, which in turn rely on the periodic tick. Since this is a rather confusing behaviour that is not easy to track down and identify for those who want to test CONFIG_NO_HZ_FULL, let's default disable the watchdog on boot time when full dynticks is enabled. The user can still enable it later on runtime using proc or sysctl. Reported-by: Steven Rostedt <rostedt@goodmis.org> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Don Zickus <dzickus@redhat.com> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Anish Singh <anish198519851985@gmail.com>
* watchdog: Rename confusing state variableFrederic Weisbecker2013-06-201-15/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We have two very conflicting state variable names in the watchdog: * watchdog_enabled: This one reflects the user interface. It's set to 1 by default and can be overriden with boot options or sysctl/procfs interface. * watchdog_disabled: This is the internal toggle state that tells if watchdog threads, timers and NMI events are currently running or not. This state mostly depends on the user settings. It's a convenient state latch. Now we really need to find clearer names because those are just too confusing to encourage deep review. watchdog_enabled now becomes watchdog_user_enabled to reflect its purpose as an interface. watchdog_disabled becomes watchdog_running to suggest its role as a pure internal state. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Anish Singh <anish198519851985@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Don Zickus <dzickus@redhat.com>
* watchdog: Register / unregister watchdog kthreads on sysctl controlFrederic Weisbecker2013-06-201-40/+47
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The user activation/deactivation of the watchdog through boot parameters or systcl is currently implemented with a dance involving kthreads parking and unparking methods: the threads are unconditionally registered on boot and they park as soon as the user want the watchdog to be disabled. This method involves a few noisy details to handle though: the watchdog kthreads may be unparked anytime due to hotplug operations, after which the watchdog internals have to decide to park again if it is user-disabled. As a result the setup() and unpark() methods need to be able to request a reparking. This is not currently supported in the kthread infrastructure so this piece of the watchdog code only works halfway. Besides, unparking/reparking the watchdog kthreads consume unnecessary cputime on hotplug operations when those could be simply ignored in the first place. As suggested by Srivatsa, let's instead only register the watchdog threads when they are needed. This way we don't need to think about hotplug operations and we don't burden the CPU onlining when the watchdog is simply disabled. Suggested-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Anish Singh <anish198519851985@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Don Zickus <dzickus@redhat.com>
* watchdog: Add comments to explain the watchdog_disabled variableanish kumar2013-03-141-0/+5
| | | | | | | | | | | | | | | | | | | The watchdog_disabled flag is a bit cryptic. However it's usefulness is multifold. Uses are: 1. Check if smpboot_register_percpu_thread function passed. 2. Makes sure that user enables and disables the watchdog in sequence i.e. enable watchdog->disable watchdog->enable watchdog Unlike enable watchdog->enable watchdog which is wrong. Signed-off-by: anish kumar <anish198519851985@gmail.com> [small text cleanups] Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: chuansheng.liu@intel.com Cc: paulmck@linux.vnet.ibm.com Link: http://lkml.kernel.org/r/1363113848-18344-1-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'core-locking-for-linus' of ↵Linus Torvalds2013-02-231-6/+4
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull core locking changes from Ingo Molnar: "The biggest change is the rwsem lock-steal improvements, both to the assembly optimized and the spinlock based variants. The other notable change is the clean up of the seqlock implementation to be based on the seqcount infrastructure. The rest is assorted smaller debuggability, cleanup and continued -rt locking changes." * 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: rwsem-spinlock: Implement writer lock-stealing for better scalability futex: Revert "futex: Mark get_robust_list as deprecated" generic: Use raw local irq variant for generic cmpxchg lockdep: Selftest: convert spinlock to raw spinlock seqlock: Use seqcount infrastructure seqlock: Remove unused functions ntp: Make ntp_lock raw intel_idle: Convert i7300_idle_lock to raw_spinlock locking: Various static lock initializer fixes lockdep: Print more info when MAX_LOCK_DEPTH is exceeded rwsem: Implement writer lock-stealing for better scalability lockdep: Silence warning if CONFIG_LOCKDEP isn't set watchdog: Use local_clock for get_timestamp() lockdep: Rename print_unlock_inbalance_bug() to print_unlock_imbalance_bug() locking/stat: Fix a typo
| * watchdog: Use local_clock for get_timestamp()Namhyung Kim2013-02-191-6/+4
| | | | | | | | | | | | | | | | | | | | | | | | The get_timestamp() function is always called with current cpu, thus using local_clock() would be more appropriate and it makes the code shorter and cleaner IMHO. Signed-off-by: Namhyung Kim <namhyung@kernel.org> Acked-by: Don Zickus <dzickus@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/1356576585-28782-1-git-send-email-namhyung@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/rt: Move rt specific bits into new header fileClark Williams2013-02-071-0/+1
|/ | | | | | | | | | | Move rt scheduler definitions out of include/linux/sched.h into new file include/linux/sched/rt.h Signed-off-by: Clark Williams <williams@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20130207094707.7b9f825f@riff.lan Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog: Fix disable/enable regressionBjørn Mork2012-12-191-7/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 8d4516904b39 ("watchdog: Fix CPU hotplug regression") causes an oops or hard lockup when doing echo 0 > /proc/sys/kernel/nmi_watchdog echo 1 > /proc/sys/kernel/nmi_watchdog and the kernel is booted with nmi_watchdog=1 (default) Running laptop-mode-tools and disconnecting/connecting AC power will cause this to trigger, making it a common failure scenario on laptops. Instead of bailing out of watchdog_disable() when !watchdog_enabled we can initialize the hrtimer regardless of watchdog_enabled status. This makes it safe to call watchdog_disable() in the nmi_watchdog=0 case, without the negative effect on the enabled => disabled => enabled case. All these tests pass with this patch: - nmi_watchdog=1 echo 0 > /proc/sys/kernel/nmi_watchdog echo 1 > /proc/sys/kernel/nmi_watchdog - nmi_watchdog=0 echo 0 > /sys/devices/system/cpu/cpu1/online - nmi_watchdog=0 echo mem > /sys/power/state Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=51661 Cc: <stable@vger.kernel.org> # v3.7 Cc: Norbert Warmuth <nwarmuth@t-online.de> Cc: Joseph Salisbury <joseph.salisbury@canonical.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Bjørn Mork <bjorn@mork.no> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* watchdog: store the watchdog sample period as a variableChuansheng Liu2012-12-181-5/+8
| | | | | | | | | | | | | Currently getting the sample period is always thru a complex calculation: get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5). We can store the sample period as a variable, and set it as __read_mostly type. Signed-off-by: liu chuansheng <chuansheng.liu@intel.com> Cc: Don Zickus <dzickus@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* watchdog: Fix CPU hotplug regressionThomas Gleixner2012-12-041-0/+3
| | | | | | | | | | | | | | | | | | | | Norbert reported: "3.7-rc6 booted with nmi_watchdog=0 fails to suspend to RAM or offline CPUs. It's reproducable with a KVM guest and physical system." The reason is that commit bcd951cf(watchdog: Use hotplug thread infrastructure) missed to take this into account. So the cpu offline code gets stuck in the teardown function because it accesses non initialized data structures. Add a check for watchdog_enabled into that path to cure the issue. Reported-and-tested-by: Norbert Warmuth <nwarmuth@t-online.de> Tested-by: Joseph Salisbury <joseph.salisbury@canonical.com> Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1211231033230.2701@ionos Link: http://bugs.launchpad.net/bugs/1079534 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* watchdog: using u64 in get_sample_period()Chuansheng Liu2012-11-271-2/+2
| | | | | | | | | | | | | | | | | | | | In get_sample_period(), unsigned long is not enough: watchdog_thresh * 2 * (NSEC_PER_SEC / 5) case1: watchdog_thresh is 10 by default, the sample value will be: 0xEE6B2800 case2: set watchdog_thresh is 20, the sample value will be: 0x1 DCD6 5000 In case2, we need use u64 to express the sample period. Otherwise, changing the threshold thru proc often can not be successful. Signed-off-by: liu chuansheng <chuansheng.liu@intel.com> Acked-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* watchdog: Use hotplug thread infrastructureThomas Gleixner2012-08-131-174/+89
| | | | | | | | | | | Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung@kernel.org> Link: http://lkml.kernel.org/r/20120716103948.563736676@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* Revert "NMI watchdog: fix for lockup detector breakage on resume"Rafael J. Wysocki2012-08-081-19/+2
| | | | | | | | | | | | | Revert commit 45226e9 (NMI watchdog: fix for lockup detector breakage on resume) which breaks resume from system suspend on my SH7372 Mackerel board (by causing a NULL pointer dereference to happen) and is generally wrong, because it abuses the CPU hotplug functionality in a shamelessly blatant way. The original issue should be addressed through appropriate syscore resume callback instead. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
* NMI watchdog: fix for lockup detector breakage on resumeSameer Nanda2012-07-311-2/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | On the suspend/resume path the boot CPU does not go though an offline->online transition. This breaks the NMI detector post-resume since it depends on PMU state that is lost when the system gets suspended. Fix this by forcing a CPU offline->online transition for the lockup detector on the boot CPU during resume. To provide more context, we enable NMI watchdog on Chrome OS. We have seen several reports of systems freezing up completely which indicated that the NMI watchdog was not firing for some reason. Debugging further, we found a simple way of repro'ing system freezes -- issuing the command 'tasket 1 sh -c "echo nmilockup > /proc/breakme"' after the system has been suspended/resumed one or more times. With this patch in place, the system freeze result in panics, as expected. These panics provide a nice stack trace for us to debug the actual issue causing the freeze. [akpm@linux-foundation.org: fiddle with code comment] [akpm@linux-foundation.org: make lockup_detector_bootcpu_resume() conditional on CONFIG_SUSPEND] [akpm@linux-foundation.org: fix section errors] Signed-off-by: Sameer Nanda <snanda@chromium.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Don Zickus <dzickus@redhat.com> Cc: Mandeep Singh Baines <msb@chromium.org> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* watchdog: Quiet down the boot messagesDon Zickus2012-06-141-1/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A bunch of bugzillas have complained how noisy the nmi_watchdog is during boot-up especially with its expected failure cases (like virt and bios resource contention). This is my attempt to quiet them down and keep it less confusing for the end user. What I did is print the message for cpu0 and save it for future comparisons. If future cpus have an identical message as cpu0, then don't print the redundant info. However, if a future cpu has a different message, happily print that loudly. Before the change, you would see something like: ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1 CPU0: Intel(R) Core(TM)2 Quad CPU Q9550 @ 2.83GHz stepping 0a Performance Events: PEBS fmt0+, Core2 events, Intel PMU driver. ... version: 2 ... bit width: 40 ... generic registers: 2 ... value mask: 000000ffffffffff ... max period: 000000007fffffff ... fixed-purpose events: 3 ... event mask: 0000000700000003 NMI watchdog enabled, takes one hw-pmu counter. Booting Node 0, Processors #1 NMI watchdog enabled, takes one hw-pmu counter. #2 NMI watchdog enabled, takes one hw-pmu counter. #3 Ok. NMI watchdog enabled, takes one hw-pmu counter. Brought up 4 CPUs Total of 4 processors activated (22607.24 BogoMIPS). After the change, it is simplified to: ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1 CPU0: Intel(R) Core(TM)2 Quad CPU Q9550 @ 2.83GHz stepping 0a Performance Events: PEBS fmt0+, Core2 events, Intel PMU driver. ... version: 2 ... bit width: 40 ... generic registers: 2 ... value mask: 000000ffffffffff ... max period: 000000007fffffff ... fixed-purpose events: 3 ... event mask: 0000000700000003 NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter. Booting Node 0, Processors #1 #2 #3 Ok. Brought up 4 CPUs V2: little changes based on Joe Perches' feedback V3: printk cleanup based on Ingo's feedback; checkpatch fix V4: keep printk as one long line V5: Ingo fix ups Reported-and-tested-by: Nathan Zimmer <nzimmer@sgi.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: nzimmer@sgi.com Cc: joe@perches.com Link: http://lkml.kernel.org/r/1339594548-17227-1-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog: add check for suspended vm in softlockup detectorEric B Munson2012-04-081-0/+12
| | | | | | | | | | | | A suspended VM can cause spurious soft lockup warnings. To avoid these, the watchdog now checks if the kernel knows it was stopped by the host and skips the warning if so. When the watchdog is reset successfully, clear the guest paused flag. Signed-off-by: Eric B Munson <emunson@mgebm.net> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
* kernel/watchdog.c: add comment to watchdog() exit pathAndrew Morton2012-03-241-0/+4
| | | | | | | | | | | Revelation from Peter. Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@tglx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* kernel/watchdog.c: convert to pr_foo()Andrew Morton2012-03-241-6/+10
| | | | | | | | | It fixes some 80-col wordwrappings and adds some consistency. Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* watchdog: make sure the watchdog thread gets CPU on loaded systemMichal Hocko2012-03-241-4/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If the system is loaded while hotplugging a CPU we might end up with a bogus hardlockup detection. This has been seen during LTP pounder test executed in parallel with hotplug test. The main problem is that enable_watchdog (called when CPU is brought up) registers perf event which periodically checks per-cpu counter (hrtimer_interrupts), updated from a hrtimer callback, but the hrtimer is fired from the kernel thread. This means that while we already do check for the hard lockup the kernel thread might be sitting on the runqueue with zillions of tasks so there is nobody to update the value we rely on and so we KABOOM. Let's fix this by boosting the watchdog thread priority before we wake it up rather than when it's already running. This still doesn't handle a case where we have the same amount of high prio FIFO tasks but that doesn't seem to be common. The current implementation doesn't handle that case anyway so this is not worse at least. Unfortunately, we cannot start perf counter from the watchdog thread because we could miss a real lock up and also we cannot start the hrtimer watchdog_enable because we there is no way (at least I don't know any) to start a hrtimer from a different CPU. [dzickus@redhat.com: fix compile issue with param] Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Reviewed-by: Mandeep Singh Baines <msb@chromium.org> Signed-off-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* watchdog: Fix code/comments mismatchesFernando Luis Vázquez Cao2012-02-111-12/+12
| | | | | | | | | | | | Reflect the change in the soft and hard lockup thresholds and their relation to the frequency of the hrtimer and NMI events in the code comments. While at it, remove references to files that do not exist anymore. Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp> Signed-off-by: Don Zickus <dzickus@redhat.com> Link: http://lkml.kernel.org/r/1328827342-6253-3-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
* bugs, x86: Fix printk levels for panic, softlockups and stack dumpsPrarit Bhargava2012-01-261-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | rsyslog will display KERN_EMERG messages on a connected terminal. However, these messages are useless/undecipherable for a general user. For example, after a softlockup we get: Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ... kernel:Stack: Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ... kernel:Call Trace: Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ... kernel:Code: ff ff a8 08 75 25 31 d2 48 8d 86 38 e0 ff ff 48 89 d1 0f 01 c8 0f ae f0 48 8b 86 38 e0 ff ff a8 08 75 08 b1 01 4c 89 e0 0f 01 c9 <e8> ea 69 dd ff 4c 29 e8 48 89 c7 e8 0f bc da ff 49 89 c4 49 89 This happens because the printk levels for these messages are incorrect. Only an informational message should be displayed on a terminal. I modified the printk levels for various messages in the kernel and tested the output by using the drivers/misc/lkdtm.c kernel modules (ie, softlockups, panics, hard lockups, etc.) and confirmed that the console output was still the same and that the output to the terminals was correct. For example, in the case of a softlockup we now see the much more informative: Message from syslogd@intel-s3e37-04 at Jan 25 10:18:06 ... BUG: soft lockup - CPU4 stuck for 60s! instead of the above confusing messages. AFAICT, the messages no longer have to be KERN_EMERG. In the most important case of a panic we set console_verbose(). As for the other less severe cases the correct data is output to the console and /var/log/messages. Successfully tested by me using the drivers/misc/lkdtm.c module. Signed-off-by: Prarit Bhargava <prarit@redhat.com> Cc: dzickus@redhat.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1327586134-11926-1-git-send-email-prarit@redhat.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
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