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Subject[tip:tracing/blktrace] blktrace: remove blk_probe_mutex
Commit-ID:  a2df44c805026d40fae556b04f9addbce486bbe2
Gitweb: http://git.kernel.org/tip/a2df44c805026d40fae556b04f9addbce486bbe2
Author: Li Zefan <lizf@cn.fujitsu.com>
AuthorDate: Fri, 20 Mar 2009 09:48:26 +0800
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 20 Mar 2009 11:20:05 +0100

blktrace: remove blk_probe_mutex

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>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49C2F5EA.8060606@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
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)
+ 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)

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