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*-. Merge branches 'consolidate.2019.08.01b', 'fixes.2019.08.12a', ↵Paul E. McKenney2019-08-132-1/+78
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | 'lists.2019.08.13a' and 'torture.2019.08.01b' into HEAD consolidate.2019.08.01b: Further consolidation cleanups fixes.2019.08.12a: Miscellaneous fixes lists.2019.08.13a: Optional lockdep arguments for RCU list macros torture.2019.08.01b: Torture-test updates
| | * treewide: Rename rcu_dereference_raw_notrace() to _check()Joel Fernandes (Google)2019-08-011-1/+1
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | The rcu_dereference_raw_notrace() API name is confusing. It is equivalent to rcu_dereference_raw() except that it also does sparse pointer checking. There are only a few users of rcu_dereference_raw_notrace(). This patches renames all of them to be rcu_dereference_raw_check() with the "_check()" indicating sparse checking. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Fix checkpatch warnings about parentheses. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * doc: Add rcutree.kthread_prio pointer to stallwarn.txtPaul E. McKenney2019-08-011-0/+6
| | | | | | | | | | | | | | | | | | This commit adds mention of the rcutree.kthread_prio kernel boot parameter to the discussion of how high-priority real-time tasks can result in RCU CPU stall warnings. (However, this does not necessarily help when the high-priority real-time tasks are using dubious deadlines.) Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Restore barrier() to rcu_read_lock() and rcu_read_unlock()Paul E. McKenney2019-08-011-0/+71
|/ | | | | | | | | | | | | | | | | | | | | | | | | | Commit bb73c52bad36 ("rcu: Don't disable preemption for Tiny and Tree RCU readers") removed the barrier() calls from rcu_read_lock() and rcu_write_lock() in CONFIG_PREEMPT=n&&CONFIG_PREEMPT_COUNT=n kernels. Within RCU, this commit was OK, but it failed to account for things like get_user() that can pagefault and that can be reordered by the compiler. Lack of the barrier() calls in rcu_read_lock() and rcu_read_unlock() can cause these page faults to migrate into RCU read-side critical sections, which in CONFIG_PREEMPT=n kernels could result in too-short grace periods and arbitrary misbehavior. Please see commit 386afc91144b ("spinlocks and preemption points need to be at least compiler barriers") and Linus's commit 66be4e66a7f4 ("rcu: locking and unlocking need to always be at least barriers"), this last of which restores the barrier() call to both rcu_read_lock() and rcu_read_unlock(). This commit removes barrier() calls that are no longer needed given that the addition of them in Linus's commit noted above. The combination of this commit and Linus's commit effectively reverts commit bb73c52bad36 ("rcu: Don't disable preemption for Tiny and Tree RCU readers"). Reported-by: Herbert Xu <herbert@gondor.apana.org.au> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> [ paulmck: Fix embarrassing typo located by Alan Stern. ]
* docs: fix broken doc references due to renamesMauro Carvalho Chehab2019-07-171-1/+1
| | | | | | | Some files got renamed but probably due to some merge conflicts, a few references still point to the old locations. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
* Merge tag 'docs-5.3' of git://git.lwn.net/linuxLinus Torvalds2019-07-095-125/+163
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull Documentation updates from Jonathan Corbet: "It's been a relatively busy cycle for docs: - A fair pile of RST conversions, many from Mauro. These create more than the usual number of simple but annoying merge conflicts with other trees, unfortunately. He has a lot more of these waiting on the wings that, I think, will go to you directly later on. - A new document on how to use merges and rebases in kernel repos, and one on Spectre vulnerabilities. - Various improvements to the build system, including automatic markup of function() references because some people, for reasons I will never understand, were of the opinion that :c:func:``function()`` is unattractive and not fun to type. - We now recommend using sphinx 1.7, but still support back to 1.4. - Lots of smaller improvements, warning fixes, typo fixes, etc" * tag 'docs-5.3' of git://git.lwn.net/linux: (129 commits) docs: automarkup.py: ignore exceptions when seeking for xrefs docs: Move binderfs to admin-guide Disable Sphinx SmartyPants in HTML output doc: RCU callback locks need only _bh, not necessarily _irq docs: format kernel-parameters -- as code Doc : doc-guide : Fix a typo platform: x86: get rid of a non-existent document Add the RCU docs to the core-api manual Documentation: RCU: Add TOC tree hooks Documentation: RCU: Rename txt files to rst Documentation: RCU: Convert RCU UP systems to reST Documentation: RCU: Convert RCU linked list to reST Documentation: RCU: Convert RCU basic concepts to reST docs: filesystems: Remove uneeded .rst extension on toctables scripts/sphinx-pre-install: fix out-of-tree build docs: zh_CN: submitting-drivers.rst: Remove a duplicated Documentation/ Documentation: PGP: update for newer HW devices Documentation: Add section about CPU vulnerabilities for Spectre Documentation: platform: Delete x86-laptop-drivers.txt docs: Note that :c:func: should no longer be used ...
| * doc: RCU callback locks need only _bh, not necessarily _irqJiunn Chang2019-06-281-6/+7
| | | | | | | | | | | | | | | | | | | | | | The UP.rst file calls for locks acquired within RCU callback functions to use _irq variants (spin_lock_irqsave() or similar), which does work, but can be overkill. This commit therefore instead calls for _bh variants (spin_lock_bh() or similar), while noting that _irq does work. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
| * Documentation: RCU: Add TOC tree hooksJiunn Chang2019-06-271-0/+19
| | | | | | | | | | | | | | | | | | | | Add TOC tree hooks for: - rcu - listRCU - UP Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
| * Documentation: RCU: Rename txt files to rstJiunn Chang2019-06-273-0/+0
| | | | | | | | | | | | | | | | | | | | Rename the following files to reST: - rcu.txt - listRCU.txt - UP.txt Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
| * Documentation: RCU: Convert RCU UP systems to reSTJiunn Chang2019-06-271-14/+23
| | | | | | | | | | | | | | | | RCU UP systems reST markup. Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
| * Documentation: RCU: Convert RCU linked list to reSTJiunn Chang2019-06-271-16/+22
| | | | | | | | | | | | | | RCU linked list reST markup. Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
| * Documentation: RCU: Convert RCU basic concepts to reSTJiunn Chang2019-06-271-58/+61
| | | | | | | | | | | | | | | | RCU basic concepts reST markup. Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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*-. \ Merge branches 'consolidate.2019.05.28a', 'doc.2019.05.28a', ↵Paul E. McKenney2019-06-193-6/+25
|\ \ \ | |_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | 'fixes.2019.06.13a', 'srcu.2019.05.28a', 'sync.2019.05.28a' and 'torture.2019.05.28a' into HEAD consolidate.2019.05.28a: RCU flavor consolidation cleanups and optmizations. doc.2019.05.28a: Documentation updates. fixes.2019.06.13a: Miscellaneous fixes. srcu.2019.05.28a: SRCU updates. sync.2019.05.28a: RCU-sync flavor consolidation. torture.2019.05.28a: Torture-test updates.
| | * rcu: Don't return a value from rcu_assign_pointer()Andrea Parri2019-06-141-4/+4
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Quoting Paul [1]: "Given that a quick (and perhaps error-prone) search of the uses of rcu_assign_pointer() in v5.1 didn't find a single use of the return value, let's please instead change the documentation and implementation to eliminate the return value." [1] https://lkml.kernel.org/r/20190523135013.GL28207@linux.ibm.com Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Cc: "Paul E. McKenney" <paulmck@linux.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: rcu@vger.kernel.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Sasha Levin <sashal@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * doc: Fixup definition of rcupdate.rcu_task_stall_timeoutZhenzhong Duan2019-05-281-1/+1
| | | | | | | | | | | | | | | | A positive value of rcupdate.rcu_task_stall_timeout is an interval in seconds rather than jiffies. Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * doc/rcuref: Document real world examples in kernelJoel Fernandes (Google)2019-05-281-1/+20
|/ | | | | | | | | | | | Document similar real world examples in the kernel corresponding to the second and third code snippets. Also correct an issue in release_referenced() in the code snippet example. Cc: oleg@redhat.com Cc: jannh@google.com Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Do a bit of wordsmithing. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Fix typos and otherwise modernize checklist.txtPaul E. McKenney2019-03-261-18/+25
| | | | | | This commit fixes some issues with Documentation/RCU/checklist.txt. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Describe choice of rcu_dereference() APIs and __rcu usagePaul E. McKenney2019-03-261-0/+103
| | | | | Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Repair some whitespace damageTycho Andersen2019-03-261-5/+5
| | | | | | | | | | A diagram in whatisRCU.txt has space character before tabs. This commit therefore makes this diagram consistent with elsewhere in the document: Use one leading tab, followed by spaces for any additional whitespace required. Signed-off-by: Tycho Andersen <tycho@tycho.ws> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Remove obsolete RCU update functions from RCU documentationPaul E. McKenney2019-03-268-76/+66
| | | | | | | | | | Now that synchronize_rcu_bh, synchronize_rcu_bh_expedited, call_rcu_bh, rcu_barrier_bh, synchronize_sched, synchronize_sched_expedited, call_rcu_sched, rcu_barrier_sched, get_state_synchronize_sched, and cond_synchronize_sched are obsolete, let's remove them from the documentation aside from a small historical section. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* Merge tag 'docs-5.1' of git://git.lwn.net/linuxLinus Torvalds2019-03-091-6/+6
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull documentation updates from Jonathan Corbet: "A fairly routine cycle for docs - lots of typo fixes, some new documents, and more translations. There's also some LICENSES adjustments from Thomas" * tag 'docs-5.1' of git://git.lwn.net/linux: (74 commits) docs: Bring some order to filesystem documentation Documentation/locking/lockdep: Drop last two chars of sample states doc: rcu: Suspicious RCU usage is a warning docs: driver-api: iio: fix errors in documentation Documentation/process/howto: Update for 4.x -> 5.x versioning docs: Explicitly state that the 'Fixes:' tag shouldn't split lines doc: security: Add kern-doc for lsm_hooks.h doc: sctp: Merge and clean up rst files Docs: Correct /proc/stat path scripts/spdxcheck.py: fix C++ comment style detection doc: fix typos in license-rules.rst Documentation: fix admin-guide/README.rst minimum gcc version requirement doc: process: complete removal of info about -git patches doc: translations: sync translations 'remove info about -git patches' perf-security: wrap paragraphs on 72 columns perf-security: elaborate on perf_events/Perf privileged users perf-security: document collected perf_events/Perf data categories perf-security: document perf_events/Perf resource control sysfs.txt: add note on available attribute macros docs: kernel-doc: typo "if ... if" -> "if ... is" ...
| * Documentation/locking/lockdep: Drop last two chars of sample statesGeert Uytterhoeven2019-03-041-3/+3
| | | | | | | | | | | | | | | | | | | | | | Since the removal of FS_RECLAIM annotations, lockdep states contain four characters, not six. Fixes: e5684bbfc3f03480 ("Documentation/locking/lockdep: Update info about states") Fixes: d92a8cfcb37ecd13 ("locking/lockdep: Rework FS_RECLAIM annotation") Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
| * doc: rcu: Suspicious RCU usage is a warningGeert Uytterhoeven2019-03-041-3/+3
| | | | | | | | | | | | | | | | | | Suspicious RCU usage messages are reported as warnings. Fixes: a5dd63efda3d07b5 ("lockdep: Use "WARNING" tag on lockdep splats") Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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*---. \ Merge branches 'doc.2019.01.26a', 'fixes.2019.01.26a', 'sil.2019.01.26a', ↵Paul E. McKenney2019-02-095-178/+13
|\ \ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 'spdx.2019.02.09a', 'srcu.2019.01.26a' and 'torture.2019.01.26a' into HEAD doc.2019.01.26a: Documentation updates. fixes.2019.01.26a: Miscellaneous fixes. sil.2019.01.26a: Removal of a few more spin_is_locked() instances. spdx.2019.02.09a: Add SPDX identifiers to RCU files srcu.2019.01.26a: SRCU updates. torture.2019.01.26a: Torture-test updates.
| | | * | RCU/torture.txt: Remove section MODULE PARAMETERSJunchang Wang2019-01-261-167/+2
| | |/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The supported module parameters are detailed in both RCU/torture.txt and admin-guide/kernel-parameters.txt, and the latter is actively maintained. So this patch removes section MODULE PARAMETERS in torture.txt and adds a reference to the information in kernel-parameters.txt. Signed-off-by: Junchang Wang <junchangwang@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> [ paulmck: Add search string. ]
| * | | rcu: Rename rcu_process_callbacks() to rcu_core() for Tree RCUPaul E. McKenney2019-01-263-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Although the name rcu_process_callbacks() still makes sense for Tiny RCU, where most of what it does is invoke callbacks, it no longer makes much sense for Tree RCU, especially given that the actually callback invocation is relegated to rcu_do_batch(), or, for no-CBs CPUs, to the rcuo kthreads. Especially in the latter case, rcu_process_callbacks() has very little to do with actual callbacks. A better description of this function is that it performs RCU's core processing. This commit therefore changes the name of Tree RCU's rcu_process_callbacks() function to rcu_core(), which also has the virtue of being consistent with the existing invoke_rcu_core() function. While in the area, the header comment is reworked. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * | | rcu: Rename rcu_check_callbacks() to rcu_sched_clock_irq()Paul E. McKenney2019-01-264-6/+6
| |/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The name rcu_check_callbacks() arguably made sense back in the early 2000s when RCU was quite a bit simpler than it is today, but it has become quite misleading, especially with the advent of dyntick-idle and NO_HZ_FULL. The rcu_check_callbacks() function is RCU's hook into the scheduling-clock interrupt, and is now but one of many ways that callbacks get promoted to invocable state. This commit therefore changes the name to rcu_sched_clock_irq(), which is the same number of characters and clearly indicates this function's relation to the rest of the Linux kernel. In addition, for the sake of consistency, rcu_flavor_check_callbacks() is also renamed to rcu_flavor_sched_clock_irq(). While in the area, the header comments for both functions are reworked. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* | | doc: Fix outdated linksJunchang Wang2019-01-261-2/+2
| | | | | | | | | | | | | | | | | | | | | Fix outdated links in whatisRCU.txt. Signed-off-by: Junchang Wang <junchangwang@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* | | doc: CPU-hotplug notifiers cannot invoke synchronize_srcu() or srcu_barrier()Paul E. McKenney2019-01-261-7/+13
|/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | SRCU's synchronize_srcu() may not be invoked from CPU-hotplug notifiers, due to the fact that SRCU grace periods make use of timers and the possibility of timers being temporarily stranded on the outgoing CPU. This stranding of timers means that timers posted to the outgoing CPU will not fire until late in the CPU-hotplug process. The problem is that if a notifier is waiting on an SRCU grace period, that grace period is waiting on a timer, and that timer is stranded on the outgoing CPU, then the notifier will never be awakened, in other words, deadlock has occurred. This same situation of course also prohibits srcu_barrier() from being invoked from CPU-hotplug notifiers. This commit therefore updates the requirements to include this restriction. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* | rcu: Discard separate per-CPU callback countsPaul E. McKenney2019-01-261-7/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Back when there were multiple flavors of RCU, it was necessary to separately count lazy and non-lazy callbacks for each CPU. These counts were used in CONFIG_RCU_FAST_NO_HZ kernels to determine how long a newly idle CPU should be allowed to sleep before handling its RCU callbacks. But now that there is only one flavor, the callback counts for a given CPU's sole rcu_data structure are the counts for that CPU. This commit therefore removes the rcu_data structure's ->nonlazy_posted and ->nonlazy_posted_snap fields, the rcu_idle_count_callbacks_posted() and rcu_cpu_has_callbacks() functions, repurposes the rcu_data structure's ->all_lazy field to record the laziness state at the beginning of the latest idle sojourn, and modifies CONFIG_RCU_FAST_NO_HZ RCU CPU stall warnings accordingly. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* | rcu: Determine expedited-GP IPI handler at build timePaul E. McKenney2019-01-262-20/+24
|/ | | | | | | | | | | | | | | Back when there could be multiple RCU flavors running in the same kernel at the same time, it was necessary to specify the expedited grace-period IPI handler at runtime. Now that there is only one RCU flavor, the IPI handler can be determined at build time. There is therefore no longer any reason for the RCU-preempt and RCU-sched IPI handlers to have different names, nor is there any reason to pass these handlers in function arguments and in the data structures enclosing workqueues. This commit therefore makes all these changes, pushing the specification of the expedited grace-period IPI handler down to the point of use. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Fix "struction" typo in RCU memory-ordering documentationJoel Fernandes (Google)2018-11-121-1/+1
| | | | | | | This commit replaces "struction" with the correct "structure". Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Correct parameter in stallwarnJoel Fernandes (Google)2018-11-121-1/+1
| | | | | | | | The stallwarn document incorrectly mentions 'fps=' instead of 'fqs='. This commit orrects that. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: RCU scheduler spinlock rcu_read_unlock() restriction remainsPaul E. McKenney2018-11-121-15/+29
| | | | | | | | | | | | | | | | Given RCU flavor consolidation, when rcu_read_unlock() is invoked with interrupts disabled, the reporting of the corresponding quiescent state is deferred until interrupts are re-enabled. There was therefore some hope that this would allow dropping the restriction against holding scheduler spinlocks across an rcu_read_unlock() without disabling interrupts across the entire corresponding RCU read-side critical section. Unfortunately, the need to quickly provide a quiescent state to expedited grace periods sometimes requires a call to raise_softirq() during rcu_read_unlock() execution. Because raise_softirq() can sometimes acquire the scheduler spinlocks, the restriction must remain in effect. This commit therefore updates the RCU requirements documentation accordingly. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Make listing in RCU perf/scale requirements use rcu_assign_pointer()Joel Fernandes (Google)2018-11-121-1/+1
| | | | | | | | | | The code listing under this section has a quick quiz that says line 19 uses rcu_access_pointer, but the code listing itself instead uses rcu_dereference(). This commit therefore makes the code listing match the quick quiz. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Remove obsolete (non-)requirement about disabling preemptionJoel Fernandes (Google)2018-11-121-50/+0
| | | | | | | | | | The Requirements.html document says "Disabling Preemption Does Not Block Grace Periods". However this is no longer true with the RCU consolidation. This commit therefore removes the obsolete (non-)requirement entirely. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Make reader aware of rcu_dereference_protectedJoel Fernandes (Google)2018-11-121-1/+14
| | | | | | | | | | | | | | The whatisRCU.txt document says rcu_dereference() cannot be used outside of rcu_read_lock() protected sections. The commit adds a mention of rcu_dereference_protected(), so that the new reader knows that this API can be used to avoid update-side use of rcu_read_lock() and rcu_read_unlock(). Cc: tytso@mit.edu Suggested-by: tytso@mit.edu Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Update wording, including further feedback from Joel. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: rcu: Encourage use of rcu_barrier in checklistJoel Fernandes (Google)2018-11-121-2/+2
| | | | | | | | | | The checklist suggests rcu_barrier_bh() for RCU-bh and similarly for sched, however these APIs are now implemented as rcu_barrier() itself due to the RCU consolidation. This commit therefore corrects checklist.txt to encourage use of the underlying rcu_barrier() API. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: rcu: Remove obsolete checklist item about synchronize_rcu usageJoel Fernandes (Google)2018-11-121-30/+7
| | | | | | | | | Since the RCU mechanisms have been consolidated, the checklist item warning that synchronize_rcu() waits only for RCU readers is obsolete. This commit therefore removes this checklist item. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: rcu: Remove obsolete suggestion from checklistJoel Fernandes (Google)2018-11-121-5/+1
| | | | | | | | | call_rcu_bh is now implemented in terms of call_rcu, so the suggestion to use a different API for speed benefits is not accurate anymore. This commit updates the document accordingly. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: rcu: Add more rationale for using rcu_read_lock_sched in checklistJoel Fernandes (Google)2018-11-121-1/+1
| | | | | | | | This commit explains why rcu_read_lock_sched is better than using preempt_disable. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: rcu: Update core and full API in whatisRCUJoel Fernandes (Google)2018-11-121-27/+28
| | | | | | | | | | | | | | | | | | | | RCU consolidation effort causes the update side of the RCU API to be consistent across all the 3 RCU flavors (normal, sched, bh). This commit therefore updates the full API in the whatisRCU document, thus encouraging people to use the consolidated RCU update API instead of the old RCU-bh and RCU-sched update APIs. Also rcu_dereference is documented to be the same for all 3 mechanisms (even before the consolidation), however its actually different - as using the right rcu_dereference primitive (such as rcu_dereference_bh for bh) is needed to make lock debugging work correctly. This update also corrects that. Also, add local_bh_disable() and local_bh_enable() as softirq protection primitives and correct a grammar error in a quiz answer. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: rcu: Update description of gp_seq fields in rcu_dataJoel Fernandes (Google)2018-11-121-3/+4
| | | | | | | | | The rcu_state structure doesn't have a gp_seq_needed field. Update the description under rcu_data accordingly, to reflect this. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: rcu: Better clarify the rcu_segcblist ->len fieldJoel Fernandes (Google)2018-11-121-8/+15
| | | | | | | | | | | An important note under the rcu_segcblist description could use a more detailed description. Especially explanation of the scenario where the ->head field may be temporarily NULL making it not wise to rely on it to determine if callbacks are associated with the rcu_segcblist. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: rcu: Update Data-Structures for RCU flavor consolidationJoel Fernandes (Google)2018-11-125-2240/+559
| | | | | | | | | | This patch updates all Data-Structures document figures and text and removes some unwanted figures, to reflect the recent work Paul has been doing with consolidating all flavors of RCU. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Remove rcu_dynticks from Data-StructuresJoel Fernandes (Google)2018-11-122-760/+25
| | | | | | | | | rcu_dynticks was folded into rcu_data structure. Update the data structures RCU document accordingly. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Update information about resched_cpuJoel Fernandes (Google)2018-11-121-3/+3
| | | | | | | | | | Since commit fced9c8cfe6b ("rcu: Avoid resched_cpu() when rescheduling the current CPU"), resched_cpu is not directly called from sync_sched_exp_handler. Update the documentation about the same. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Remove rcu_preempt_state reference in stallwarnJoel Fernandes (Google)2018-11-091-3/+2
| | | | | | | | | | | Consolidation of RCU-bh, RCU-preempt, and RCU-sched into one RCU flavor to rule them all resulted in the removal of rcu_preempt_state. However, stallwarn.txt still mentions rcu_preempt_state. This commit therefore Updates stallwarn documentation accordingly. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Clarify RCU data-structure comment about rcu_tree fanoutJoel Fernandes (Google)2018-11-091-3/+5
| | | | | | | | | | | | RCU Data-Structures document describes a trick to test RCU with small number of CPUs but with a taller tree. It wasn't immediately clear how the document arrived at 16 CPUs which also requires setting the FANOUT_LEAF to 2 instead of the default of 16. This commit therefore provides the needed clarification. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* doc: Set down forward-progress requirementsPaul E. McKenney2018-11-091-2/+108
| | | | | | | This commit adds a section to the requirements documentation setting down requirements for grace-period and callback-invocation forward progress. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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