Patch 8bb39f9 (perf: Fix 'perf sched record' deadlock) introduced a local_irq_save() in NMI context, convert that to local_irq_save_nmi() and move the IRQ disable into perf_output_lock/unlock(). The former is needed because we now disallow local_irq_disable() from NMI context due to some arch limitations. The second is because its really about IRQ lock inversion with that funny output lock, and perf_event_task_output() is only one site that could trigger it. Signed-off-by: Peter Zijlstra Cc: Mike Galbraith --- include/linux/perf_event.h | 1 + kernel/perf_event.c | 17 ++++++----------- 2 files changed, 7 insertions(+), 11 deletions(-) Index: linux-2.6/include/linux/perf_event.h =================================================================== --- linux-2.6.orig/include/linux/perf_event.h +++ linux-2.6/include/linux/perf_event.h @@ -758,6 +758,7 @@ struct perf_output_handle { struct perf_mmap_data *data; unsigned long head; unsigned long offset; + unsigned long flags; int nmi; int sample; int locked; Index: linux-2.6/kernel/perf_event.c =================================================================== --- linux-2.6.orig/kernel/perf_event.c +++ linux-2.6/kernel/perf_event.c @@ -2848,6 +2848,10 @@ static void perf_output_lock(struct perf struct perf_mmap_data *data = handle->data; int cur, cpu = get_cpu(); + /* + * Since this is a lock we need to be IRQ-safe + */ + local_irq_save_nmi(handle->flags); handle->locked = 0; for (;;) { @@ -2906,6 +2910,7 @@ again: if (atomic_xchg(&data->wakeup, 0)) perf_output_wakeup(handle); out: + local_irq_restore_nmi(handle->flags); put_cpu(); } @@ -3385,19 +3390,10 @@ static void perf_event_task_output(struc unsigned long flags; int size, ret; - /* - * If this CPU attempts to acquire an rq lock held by a CPU spinning - * in perf_output_lock() from interrupt context, it's game over. - */ - local_irq_save(flags); - size = task_event->event_id.header.size; ret = perf_output_begin(&handle, event, size, 0, 0); - - if (ret) { - local_irq_restore(flags); + if (ret) return; - } task_event->event_id.pid = perf_event_pid(event, task); task_event->event_id.ppid = perf_event_pid(event, current); @@ -3408,7 +3404,6 @@ static void perf_event_task_output(struc perf_output_put(&handle, task_event->event_id); perf_output_end(&handle); - local_irq_restore(flags); } static int perf_event_task_match(struct perf_event *event) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/