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| author | Vineet Gupta <vgupta@synopsys.com> | 2018-12-18 19:39:58 +0100 |
|---|---|---|
| committer | Vineet Gupta <vgupta@synopsys.com> | 2019-01-17 23:38:00 +0100 |
| commit | f731a8e89f8c78985707c626680f3e24c7a60772 (patch) | |
| tree | 7766124bcf5dc4d495fae018b0ea24ada1241317 /arch | |
| parent | ARC: show_regs: lockdep: avoid page allocator... (diff) | |
| download | linux-f731a8e89f8c78985707c626680f3e24c7a60772.tar.xz linux-f731a8e89f8c78985707c626680f3e24c7a60772.zip | |
ARC: show_regs: lockdep: re-enable preemption
signal handling core calls show_regs() with preemption disabled which
on ARC takes mmap_sem for mm/vma access, causing lockdep splat.
| [ARCLinux]# ./segv-null-ptr
| potentially unexpected fatal signal 11.
| BUG: sleeping function called from invalid context at kernel/fork.c:1011
| in_atomic(): 1, irqs_disabled(): 0, pid: 70, name: segv-null-ptr
| no locks held by segv-null-ptr/70.
| CPU: 0 PID: 70 Comm: segv-null-ptr Not tainted 4.18.0+ #69
|
| Stack Trace:
| arc_unwind_core+0xcc/0x100
| ___might_sleep+0x17a/0x190
| mmput+0x16/0xb8
| show_regs+0x52/0x310
| get_signal+0x5ee/0x610
| do_signal+0x2c/0x218
| resume_user_mode_begin+0x90/0xd8
Workaround by re-enabling preemption temporarily.
Note that the preemption disabling in core code around show_regs()
was introduced by commit 3a9f84d354ce ("signals, debug: fix BUG: using
smp_processor_id() in preemptible code in print_fatal_signal()")
to silence a differnt lockdep seen on x86 bakc in 2009.
Cc: <stable@vger.kernel.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arc/kernel/troubleshoot.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c index 5c6663321e87..215f515442e0 100644 --- a/arch/arc/kernel/troubleshoot.c +++ b/arch/arc/kernel/troubleshoot.c @@ -179,6 +179,12 @@ void show_regs(struct pt_regs *regs) struct task_struct *tsk = current; struct callee_regs *cregs; + /* + * generic code calls us with preemption disabled, but some calls + * here could sleep, so re-enable to avoid lockdep splat + */ + preempt_enable(); + print_task_path_n_nm(tsk); show_regs_print_info(KERN_INFO); @@ -221,6 +227,8 @@ void show_regs(struct pt_regs *regs) cregs = (struct callee_regs *)current->thread.callee_reg; if (cregs) show_callee_regs(cregs); + + preempt_disable(); } void show_kernel_fault_diag(const char *str, struct pt_regs *regs, |