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| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2015-08-16 14:27:50 +0200 |
|---|---|---|
| committer | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2016-02-13 00:36:19 +0100 |
| commit | b4f830750ef6c90ae2ed2a60a5c90e489773e712 (patch) | |
| tree | a87e02dbb2e53357c9eed12ce797720774f73747 | |
| parent | 862622197f8c5f5dc178809fb270130af14f3ef7 (diff) | |
| download | rt-linux-b4f830750ef6c90ae2ed2a60a5c90e489773e712.tar.gz | |
dump stack: don't disable preemption during trace
I see here large latencies during a stack dump on x86. The
preempt_disable() and get_cpu() should forbid moving the task to another
CPU during a stack dump and avoiding two stack traces in parallel on the
same CPU. However a stack trace from a second CPU may still happen in
parallel. Also nesting is allowed so a stack trace happens in
process-context and we may have another one from IRQ context. With migrate
disable we keep this code preemptible and allow a second backtrace on
the same CPU by another task.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
| -rw-r--r-- | arch/x86/kernel/dumpstack_32.c | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/dumpstack_64.c | 8 | ||||
| -rw-r--r-- | lib/dump_stack.c | 4 |
3 files changed, 8 insertions, 8 deletions
diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c index 464ffd69b92e9e..00db1aad1548f5 100644 --- a/arch/x86/kernel/dumpstack_32.c +++ b/arch/x86/kernel/dumpstack_32.c @@ -42,7 +42,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, unsigned long *stack, unsigned long bp, const struct stacktrace_ops *ops, void *data) { - const unsigned cpu = get_cpu(); + const unsigned cpu = get_cpu_light(); int graph = 0; u32 *prev_esp; @@ -86,7 +86,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, break; touch_nmi_watchdog(); } - put_cpu(); + put_cpu_light(); } EXPORT_SYMBOL(dump_trace); diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c index 5f1c6266eb3028..c331e3fef46547 100644 --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -152,7 +152,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, unsigned long *stack, unsigned long bp, const struct stacktrace_ops *ops, void *data) { - const unsigned cpu = get_cpu(); + const unsigned cpu = get_cpu_light(); struct thread_info *tinfo; unsigned long *irq_stack = (unsigned long *)per_cpu(irq_stack_ptr, cpu); unsigned long dummy; @@ -241,7 +241,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, * This handles the process stack: */ bp = ops->walk_stack(tinfo, stack, bp, ops, data, NULL, &graph); - put_cpu(); + put_cpu_light(); } EXPORT_SYMBOL(dump_trace); @@ -255,7 +255,7 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs, int cpu; int i; - preempt_disable(); + migrate_disable(); cpu = smp_processor_id(); irq_stack_end = (unsigned long *)(per_cpu(irq_stack_ptr, cpu)); @@ -291,7 +291,7 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs, pr_cont(" %016lx", *stack++); touch_nmi_watchdog(); } - preempt_enable(); + migrate_enable(); pr_cont("\n"); show_trace_log_lvl(task, regs, sp, bp, log_lvl); diff --git a/lib/dump_stack.c b/lib/dump_stack.c index 6745c6230db340..7ccbc6ff80eac1 100644 --- a/lib/dump_stack.c +++ b/lib/dump_stack.c @@ -33,7 +33,7 @@ asmlinkage __visible void dump_stack(void) * Permit this cpu to perform nested stack dumps while serialising * against other CPUs */ - preempt_disable(); + migrate_disable(); retry: cpu = smp_processor_id(); @@ -52,7 +52,7 @@ retry: if (!was_locked) atomic_set(&dump_lock, -1); - preempt_enable(); + migrate_enable(); } #else asmlinkage __visible void dump_stack(void) |