Messages in this thread Patch in this message | | | Date | Mon, 30 Mar 2009 01:19:41 GMT | From | Li Zefan <> | Subject | [tip:tracing/blktrace] blktrace: fix blk_probes_ref chaos |
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Commit-ID: e465dbcc55d36b37af55d95a279f352a3f517279 Gitweb: http://git.kernel.org/tip/e465dbcc55d36b37af55d95a279f352a3f517279 Author: Li Zefan <lizf@cn.fujitsu.com> AuthorDate: Fri, 27 Mar 2009 10:20:09 +0800 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Mon, 30 Mar 2009 03:15:50 +0200
blktrace: fix blk_probes_ref chaos
Impact: fix mixed ioctl and ftrace-plugin blktrace use refcount bugs
ioctl-based blktrace allocates bt and registers tracepoints when ioctl(BLKTRACESETUP), and do all cleanups when ioctl(BLKTRACETEARDOWN).
while ftrace-based blktrace allocates/frees bt when: # echo 1/0 > /sys/block/sda/sda1/trace/enable
and registers/unregisters tracepoints when: # echo blk/nop > /debugfs/tracing/current_tracer or # echo 1/0 > /debugfs/tracing/tracing_enable
The separatation of allocation and registeration causes 2 problems:
1. current user-space blktrace still calls ioctl(TEARDOWN) when ioctl(SETUP) failed: # echo 1 > /sys/block/sda/sda1/trace/enable # blktrace /dev/sda BLKTRACESETUP: Device or resource busy ^C and now blk_probes_ref == -1
2. Another way to make blk_probes_ref == -1: # plugin sdb && mount sdb1 # echo 1 > /sys/block/sdb/sdb1/trace/enable # remove sdb
This patch does the allocation and registeration when writing sdaX/trace/enable.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Jens Axboe <jens.axboe@oracle.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <49CC37D9.6030201@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
--- kernel/trace/blktrace.c | 15 +++++++-------- 1 files changed, 7 insertions(+), 8 deletions(-)
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 5b28f0f..8d6bd12 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -478,7 +478,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, goto err; } - if (atomic_add_return(1, &blk_probes_ref) == 1) + if (atomic_inc_return(&blk_probes_ref) == 1) blk_register_tracepoints(); return 0; @@ -1091,8 +1091,6 @@ static void blk_tracer_print_header(struct seq_file *m) static void blk_tracer_start(struct trace_array *tr) { - if (atomic_add_return(1, &blk_probes_ref) == 1) - blk_register_tracepoints(); trace_flags &= ~TRACE_ITER_CONTEXT_INFO; } @@ -1107,15 +1105,10 @@ static int blk_tracer_init(struct trace_array *tr) static void blk_tracer_stop(struct trace_array *tr) { trace_flags |= TRACE_ITER_CONTEXT_INFO; - if (atomic_dec_and_test(&blk_probes_ref)) - blk_unregister_tracepoints(); } static void blk_tracer_reset(struct trace_array *tr) { - if (!atomic_read(&blk_probes_ref)) - return; - blk_tracer_enabled = false; blk_tracer_stop(tr); } @@ -1254,6 +1247,9 @@ static int blk_trace_remove_queue(struct request_queue *q) if (bt == NULL) return -EINVAL; + if (atomic_dec_and_test(&blk_probes_ref)) + blk_unregister_tracepoints(); + kfree(bt); return 0; } @@ -1280,6 +1276,9 @@ static int blk_trace_setup_queue(struct request_queue *q, dev_t dev) return -EBUSY; } + if (atomic_inc_return(&blk_probes_ref) == 1) + blk_register_tracepoints(); + return 0; }
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