Currently if arch_trigger_all_cpu_backtrace() is called with interrupts disabled and on a platform the delivers IPI_CPU_BACKTRACE using regular IRQ requests the system will wedge for ten seconds waiting for the current CPU to react to a masked interrupt.
This patch resolves this issue by calling directly into the backtrace dump code instead of generating an IPI.
Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Steven Rostedt rostedt@goodmis.org --- arch/arm/kernel/smp.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index afb094a1e6d4..cf3b738568b8 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -742,6 +742,16 @@ void arch_trigger_all_cpu_backtrace(bool include_self) cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask)); cpumask_copy(&printtrace_mask, to_cpumask(backtrace_mask));
+ /* + * If irqs are disabled on the current processor then, if + * IPI_CPU_BACKTRACE is delivered using IRQ, we will won't be able to + * react to IPI_CPU_BACKTRACE until we leave this function. We avoid + * the potential timeout (not to mention the failure to print useful + * information) by calling the backtrace directly. + */ + if (include_self && irqs_disabled()) + ipi_cpu_backtrace(in_interrupt() ? get_irq_regs() : NULL); + if (!cpumask_empty(to_cpumask(backtrace_mask))) { pr_info("Sending FIQ to %s CPUs:\n", (include_self ? "all" : "other")); @@ -770,7 +780,10 @@ void ipi_cpu_backtrace(struct pt_regs *regs) if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { orig = this_cpu_begin_nmi_printk(); pr_warn("FIQ backtrace for cpu %d\n", cpu); - show_regs(regs); + if (regs != NULL) + show_regs(regs); + else + dump_stack(); this_cpu_end_nmi_printk(orig);
cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));