SysRq-L and RCU stall detector call arch_trigger_cpumask_backtrace() to
trigger other CPU's backtrace, but its behavior is totally broken. The
root cause is arch_trigger_cpumask_backtrace() use call-function IPI in
irq context, which trigger deadlocks in smp_call_function_single() and
smp_call_function_many().
This patch fix arch_trigger_cpumask_backtrace() by:
1, Use a dedecated IPI (SMP_CPU_BACKTRACE) to trigger backtraces;
2, If myself is in target cpumask, do backtrace and clear myself;
3, Use a spinlock to avoid parallel backtrace output;
4, Handle SMP_CPU_BACKTRACE IPI for Loongson-3.
I have attempted to implement SMP_CPU_BACKTRACE for all MIPS CPUs, but I
failed because some of their IPIs are not extensible. :(
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Huacai Chen <chenhc@xxxxxxxxxx>
---
arch/mips/include/asm/smp.h | 3 +++
arch/mips/kernel/process.c | 23 ++++++++++++++++++-----
arch/mips/loongson64/loongson-3/smp.c | 6 ++++++
3 files changed, 27 insertions(+), 5 deletions(-)
diff --git a/arch/mips/include/asm/smp.h b/arch/mips/include/asm/smp.h
index 88ebd83..b0521f4 100644
--- a/arch/mips/include/asm/smp.h
+++ b/arch/mips/include/asm/smp.h
@@ -43,6 +43,7 @@ extern int __cpu_logical_map[NR_CPUS];
/* Octeon - Tell another core to flush its icache */
#define SMP_ICACHE_FLUSH 0x4
#define SMP_ASK_C0COUNT 0x8
+#define SMP_CPU_BACKTRACE 0x10
/* Mask of CPUs which are currently definitely operating coherently */
extern cpumask_t cpu_coherent_mask;
@@ -81,6 +82,8 @@ static inline void __cpu_die(unsigned int cpu)
extern void play_dead(void);
#endif
+void arch_dump_stack(void);
+
/*
* This function will set up the necessary IPIs for Linux to communicate
* with the CPUs in mask.
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 57028d4..647e15d 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -655,26 +655,39 @@ unsigned long arch_align_stack(unsigned long sp)
return sp & ALMASK;
}
-static void arch_dump_stack(void *info)
+void arch_dump_stack(void)
{
struct pt_regs *regs;
+ static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
+ arch_spin_lock(&lock);
regs = get_irq_regs();
if (regs)
show_regs(regs);
dump_stack();
+ arch_spin_unlock(&lock);
}
void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
{
long this_cpu = get_cpu();
+ struct cpumask backtrace_mask;
+ extern const struct plat_smp_ops *mp_ops;
+
+ cpumask_copy(&backtrace_mask, mask);
+ if (cpumask_test_cpu(this_cpu, mask)) {
+ if (!exclude_self) {
+ struct pt_regs *regs = get_irq_regs();
+ if (regs)
+ show_regs(regs);
+ dump_stack();
+ }
+ cpumask_clear_cpu(this_cpu, &backtrace_mask);
+ }
- if (cpumask_test_cpu(this_cpu, mask) && !exclude_self)
- dump_stack();
-
- smp_call_function_many(mask, arch_dump_stack, NULL, 1);
+ mp_ops->send_ipi_mask(&backtrace_mask, SMP_CPU_BACKTRACE);
put_cpu();
}
diff --git a/arch/mips/loongson64/loongson-3/smp.c b/arch/mips/loongson64/loongson-3/smp.c
index 8501109..0655114 100644
--- a/arch/mips/loongson64/loongson-3/smp.c
+++ b/arch/mips/loongson64/loongson-3/smp.c
@@ -291,6 +291,12 @@ void loongson3_ipi_interrupt(struct pt_regs *regs)
__wbflush(); /* Let others see the result ASAP */
}
+ if (action & SMP_CPU_BACKTRACE) {
+ irq_enter();
+ arch_dump_stack();
+ irq_exit();
+ }
+
if (irqs) {
int irq;
while ((irq = ffs(irqs))) {
--
2.7.0
