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SubjectRe: [PATCH 3/7] blktrace: remove blk_probe_mutex
On Fri, Mar 20, 2009 at 09:48:26AM +0800, Li Zefan wrote:
> blk_register_tracepoints() always returns 0, so make it return void, thus
> we don't need to use blk_probe_mutex to protect blk_probes_ref.
>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> ---
> kernel/trace/blktrace.c | 27 +++++----------------------
> 1 files changed, 5 insertions(+), 22 deletions(-)
>
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index 73845b7..223b92e 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -47,10 +47,9 @@ static struct tracer_flags blk_tracer_flags = {
> };
>
> /* Global reference count of probes */
> -static DEFINE_MUTEX(blk_probe_mutex);
> static atomic_t blk_probes_ref = ATOMIC_INIT(0);
>
> -static int blk_register_tracepoints(void);
> +static void blk_register_tracepoints(void);
> static void blk_unregister_tracepoints(void);
>
> /*
> @@ -256,10 +255,8 @@ static void blk_trace_cleanup(struct blk_trace *bt)
> free_percpu(bt->sequence);
> free_percpu(bt->msg_data);
> kfree(bt);
> - mutex_lock(&blk_probe_mutex);
> if (atomic_dec_and_test(&blk_probes_ref))
> blk_unregister_tracepoints();
> - mutex_unlock(&blk_probe_mutex);
> }
>
> int blk_trace_remove(struct request_queue *q)
> @@ -471,13 +468,8 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
> bt->pid = buts->pid;
> bt->trace_state = Blktrace_setup;
>
> - mutex_lock(&blk_probe_mutex);
> - if (atomic_add_return(1, &blk_probes_ref) == 1) {
> - ret = blk_register_tracepoints();
> - if (ret)
> - goto probe_err;
> - }
> - mutex_unlock(&blk_probe_mutex);
> + if (atomic_add_return(1, &blk_probes_ref) == 1)


atomic_inc_return() is a bit more simple.


> + blk_register_tracepoints();
>
> ret = -EBUSY;
> old_bt = xchg(&q->blk_trace, bt);
> @@ -487,9 +479,6 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
> }
>
> return 0;
> -probe_err:
> - atomic_dec(&blk_probes_ref);
> - mutex_unlock(&blk_probe_mutex);
> err:
> if (bt) {
> if (bt->msg_file)
> @@ -863,7 +852,7 @@ void blk_add_driver_data(struct request_queue *q,
> }
> EXPORT_SYMBOL_GPL(blk_add_driver_data);
>
> -static int blk_register_tracepoints(void)
> +static void blk_register_tracepoints(void)
> {
> int ret;
>
> @@ -901,7 +890,6 @@ static int blk_register_tracepoints(void)
> WARN_ON(ret);
> ret = register_trace_block_remap(blk_add_trace_remap);
> WARN_ON(ret);
> - return 0;
> }
>
> static void blk_unregister_tracepoints(void)
> @@ -1099,11 +1087,8 @@ static void blk_tracer_print_header(struct seq_file *m)
>
> static void blk_tracer_start(struct trace_array *tr)
> {
> - mutex_lock(&blk_probe_mutex);
> if (atomic_add_return(1, &blk_probes_ref) == 1)
> - if (blk_register_tracepoints())
> - atomic_dec(&blk_probes_ref);
> - mutex_unlock(&blk_probe_mutex);
> + blk_register_tracepoints();
> trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
> }
>
> @@ -1118,10 +1103,8 @@ static int blk_tracer_init(struct trace_array *tr)
> static void blk_tracer_stop(struct trace_array *tr)
> {
> trace_flags |= TRACE_ITER_CONTEXT_INFO;
> - mutex_lock(&blk_probe_mutex);
> if (atomic_dec_and_test(&blk_probes_ref))
> blk_unregister_tracepoints();
> - mutex_unlock(&blk_probe_mutex);
> }
>
> static void blk_tracer_reset(struct trace_array *tr)
> --
> 1.5.4.rc3
>

Looks good.



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