From 361c81dbc58c8aa230e1f2d556045fa7bc3eb4a3 Mon Sep 17 00:00:00 2001 From: Wander Lairson Costa Date: Mon, 20 Dec 2021 16:28:27 -0300 Subject: [PATCH] blktrace: switch trace spinlock to a raw spinlock The running_trace_lock protects running_trace_list and is acquired within the tracepoint which implies disabled preemption. The spinlock_t typed lock can not be acquired with disabled preemption on PREEMPT_RT because it becomes a sleeping lock. The runtime of the tracepoint depends on the number of entries in running_trace_list and has no limit. The blk-tracer is considered debug code and higher latencies here are okay. Make running_trace_lock a raw_spinlock_t. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20211220192827.38297-1-wander@redhat.com Signed-off-by: Jens Axboe --- kernel/trace/blktrace.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 431e41bc4c23..af68a67179b4 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -34,7 +34,7 @@ static struct trace_array *blk_tr; static bool blk_tracer_enabled __read_mostly; static LIST_HEAD(running_trace_list); -static __cacheline_aligned_in_smp DEFINE_SPINLOCK(running_trace_lock); +static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(running_trace_lock); /* Select an alternative, minimalistic output than the original one */ #define TRACE_BLK_OPT_CLASSIC 0x1 @@ -121,12 +121,12 @@ static void trace_note_tsk(struct task_struct *tsk) struct blk_trace *bt; tsk->btrace_seq = blktrace_seq; - spin_lock_irqsave(&running_trace_lock, flags); + raw_spin_lock_irqsave(&running_trace_lock, flags); list_for_each_entry(bt, &running_trace_list, running_list) { trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm, sizeof(tsk->comm), 0); } - spin_unlock_irqrestore(&running_trace_lock, flags); + raw_spin_unlock_irqrestore(&running_trace_lock, flags); } static void trace_note_time(struct blk_trace *bt) @@ -666,9 +666,9 @@ static int __blk_trace_startstop(struct request_queue *q, int start) blktrace_seq++; smp_mb(); bt->trace_state = Blktrace_running; - spin_lock_irq(&running_trace_lock); + raw_spin_lock_irq(&running_trace_lock); list_add(&bt->running_list, &running_trace_list); - spin_unlock_irq(&running_trace_lock); + raw_spin_unlock_irq(&running_trace_lock); trace_note_time(bt); ret = 0; @@ -676,9 +676,9 @@ static int __blk_trace_startstop(struct request_queue *q, int start) } else { if (bt->trace_state == Blktrace_running) { bt->trace_state = Blktrace_stopped; - spin_lock_irq(&running_trace_lock); + raw_spin_lock_irq(&running_trace_lock); list_del_init(&bt->running_list); - spin_unlock_irq(&running_trace_lock); + raw_spin_unlock_irq(&running_trace_lock); relay_flush(bt->rchan); ret = 0; } @@ -1608,9 +1608,9 @@ static int blk_trace_remove_queue(struct request_queue *q) if (bt->trace_state == Blktrace_running) { bt->trace_state = Blktrace_stopped; - spin_lock_irq(&running_trace_lock); + raw_spin_lock_irq(&running_trace_lock); list_del_init(&bt->running_list); - spin_unlock_irq(&running_trace_lock); + raw_spin_unlock_irq(&running_trace_lock); relay_flush(bt->rchan); } -- 2.11.0