path: root/arch/arm/kernel/smp.c
diff options
authorDaniel Thompson <daniel.thompson@linaro.org>2015-09-22 17:12:10 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2015-10-03 16:40:51 +0100
commit0768330d46435f324a0b4860c889057524af17c2 (patch)
tree1a7edb29ee41d640e92c67ea7a7ae910e902dd3e /arch/arm/kernel/smp.c
parent001bf455d20645190beb98ff4ee450dfea1b7eb2 (diff)
ARM: 8439/1: Fix backtrace generation when IPI is masked
Currently on ARM when <SysRq-L> is triggered from an interrupt handler (e.g. a SysRq issued using UART or kbd) the main CPU will wedge for ten seconds with interrupts masked before issuing a backtrace for every CPU except itself. The new backtrace code introduced by commit 96f0e00378d4 ("ARM: add basic support for on-demand backtrace of other CPUs") does not work correctly when run from an interrupt handler because IPI_CPU_BACKTRACE is used to generate the backtrace on all CPUs but cannot preempt the current calling context. This can be fixed by detecting that the calling context cannot be preempted and issuing the backtrace directly in this case. Issuing directly leaves us without any pt_regs to pass to nmi_cpu_backtrace() so we also modify the generic code to call dump_stack() when its argument is NULL. Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/smp.c')
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 7c467c5b048e..b26361355dae 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -749,6 +749,15 @@ core_initcall(register_cpufreq_notifier);
static void raise_nmi(cpumask_t *mask)
+ /*
+ * Generate the backtrace directly if we are running in a calling
+ * context that is not preemptible by the backtrace IPI. Note
+ * that nmi_cpu_backtrace() automatically removes the current cpu
+ * from mask.
+ */
+ if (cpumask_test_cpu(smp_processor_id(), mask) && irqs_disabled())
+ nmi_cpu_backtrace(NULL);
smp_cross_call(mask, IPI_CPU_BACKTRACE);