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| author | Paul E. McKenney <paulmck@kernel.org> | 2020-07-08 16:25:43 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-08-24 14:24:25 -0700 |
| commit | 160c7ba34605d9b59ee406a1b4a61b0f942b1ae9 (patch) | |
| tree | 6bb20cf2018927bc9fd28b8357a3e7d0410e06fc | |
| parent | 9123e3a74ec7b934a4a099e98af6a61c2f80bbf5 (diff) | |
| download | linux-stable-160c7ba34605d9b59ee406a1b4a61b0f942b1ae9.tar.gz linux-stable-160c7ba34605d9b59ee406a1b4a61b0f942b1ae9.tar.bz2 linux-stable-160c7ba34605d9b59ee406a1b4a61b0f942b1ae9.zip | |
lib: Add backtrace_idle parameter to force backtrace of idle CPUs
Currently, the nmi_cpu_backtrace() declines to produce backtraces for
idle CPUs. This is a good choice in the common case in which problems are
caused only by non-idle CPUs. However, there are occasionally situations
in which idle CPUs are helping to cause problems. This commit therefore
adds an nmi_backtrace.backtrace_idle kernel boot parameter that causes
nmi_cpu_backtrace() to dump stacks even of idle CPUs.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: <linux-doc@vger.kernel.org>
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 4 | ||||
| -rw-r--r-- | lib/nmi_backtrace.c | 6 |
2 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index bdc1f33fd3d1..5e6d19182c5f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3073,6 +3073,10 @@ and gids from such clients. This is intended to ease migration from NFSv2/v3. + nmi_backtrace.backtrace_idle [KNL] + Dump stacks even of idle CPUs in response to an + NMI stack-backtrace request. + nmi_debug= [KNL,SH] Specify one or more actions to take when a NMI is triggered. Format: [state][,regs][,debounce][,die] diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c index 15ca78e1c7d4..8abe1870dba4 100644 --- a/lib/nmi_backtrace.c +++ b/lib/nmi_backtrace.c @@ -85,12 +85,16 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, put_cpu(); } +// Dump stacks even for idle CPUs. +static bool backtrace_idle; +module_param(backtrace_idle, bool, 0644); + bool nmi_cpu_backtrace(struct pt_regs *regs) { int cpu = smp_processor_id(); if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { - if (regs && cpu_in_idle(instruction_pointer(regs))) { + if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) { pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n", cpu, (void *)instruction_pointer(regs)); } else { |