3.2.77-rt111-rc1 stable review patch. If anyone has any objections, please let me know.
------------------ From: Sebastian Andrzej Siewior <[email protected]> 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 <[email protected]> Signed-off-by: Steven Rostedt <[email protected]> --- arch/x86/kernel/dumpstack_64.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c index 5e890ccd5429..530fdb80d250 100644 --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -114,7 +114,7 @@ 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(); unsigned long *irq_stack_end = (unsigned long *)per_cpu(irq_stack_ptr, cpu); unsigned used = 0; @@ -191,7 +191,7 @@ 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); @@ -205,7 +205,7 @@ 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)); @@ -238,7 +238,7 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs, printk(KERN_CONT " %016lx", *stack++); touch_nmi_watchdog(); } - preempt_enable(); + migrate_enable(); printk(KERN_CONT "\n"); show_trace_log_lvl(task, regs, sp, bp, log_lvl); -- 2.7.0
