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authorWander Lairson Costa <wander@redhat.com>2021-12-20 16:28:27 -0300
committerJens Axboe <axboe@kernel.dk>2021-12-20 13:50:14 -0700
commit361c81dbc58c8aa230e1f2d556045fa7bc3eb4a3 (patch)
treece8ee18c100f6ddaedfb01f8da170c7d958dd591
parent5ef1630586317e92c9ebd7b4ce48f393b7ff790f (diff)
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 <wander@redhat.com> Link: https://lore.kernel.org/r/20211220192827.38297-1-wander@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--kernel/trace/blktrace.c18
1 files 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);
}