[PATCH 3.19-rc2 v13 5/5] ARM: Fix on-demand backtrace triggered by IRQ
From: Daniel Thompson <hidden>
Date: 2015-01-05 14:55:24
Also in:
lkml
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
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 <redacted> 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 12667eb68198..644f654f7a7e 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c@@ -767,7 +767,10 @@ void ipi_cpu_backtrace(struct pt_regs *regs) /* Replace printk to write into the NMI seq */ this_cpu_write(printk_func, nmi_vprintk); printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu); - show_regs(regs); + if (regs != NULL) + show_regs(regs); + else + dump_stack(); this_cpu_write(printk_func, printk_func_save); cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
@@ -812,6 +815,16 @@ void arch_trigger_all_cpu_backtrace(bool include_self) seq_buf_init(&s->seq, s->buffer, NMI_BUF_SIZE); } + /* + * 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 NMI to %s CPUs:\n", (include_self ? "all" : "other"));
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1.9.3