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author | Robert Richter <robert.richter@amd.com> | 2009-10-09 03:17:44 +0200 |
---|---|---|
committer | Robert Richter <robert.richter@amd.com> | 2009-10-09 21:32:05 +0200 |
commit | c0868934e536e0ff508f2d359d006b25abc4970d (patch) | |
tree | 54932dfb00ee6731a1d3421eba1a87ed025f72dd /drivers/oprofile/event_buffer.c | |
parent | 066b3aa8454bee3cdc665d86b5de812d8d0513b3 (diff) | |
download | linux-stable-c0868934e536e0ff508f2d359d006b25abc4970d.tar.gz linux-stable-c0868934e536e0ff508f2d359d006b25abc4970d.tar.bz2 linux-stable-c0868934e536e0ff508f2d359d006b25abc4970d.zip |
oprofile: warn on freeing event buffer too early
A race shouldn't happen since all workqueues or handlers are canceled
or flushed before the event buffer is freed. A warning is triggered
now if the buffer is freed too early.
Also, this patch adds some comments about event buffer protection,
reworks some code and adds code to clear buffer_pos during alloc and
free of the event buffer.
Cc: David Rientjes <rientjes@google.com>
Cc: Stephane Eranian <eranian@google.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>
Diffstat (limited to 'drivers/oprofile/event_buffer.c')
-rw-r--r-- | drivers/oprofile/event_buffer.c | 25 |
1 files changed, 15 insertions, 10 deletions
diff --git a/drivers/oprofile/event_buffer.c b/drivers/oprofile/event_buffer.c index c38adb389064..5df60a6b6776 100644 --- a/drivers/oprofile/event_buffer.c +++ b/drivers/oprofile/event_buffer.c @@ -35,17 +35,22 @@ static size_t buffer_pos; /* atomic_t because wait_event checks it outside of buffer_mutex */ static atomic_t buffer_ready = ATOMIC_INIT(0); -/* Add an entry to the event buffer. When we - * get near to the end we wake up the process - * sleeping on the read() of the file. +/* + * Add an entry to the event buffer. When we get near to the end we + * wake up the process sleeping on the read() of the file. To protect + * the event_buffer this function may only be called when buffer_mutex + * is set. */ void add_event_entry(unsigned long value) { /* - * catch potential error + * This shouldn't happen since all workqueues or handlers are + * canceled or flushed before the event buffer is freed. */ - if (!event_buffer) + if (!event_buffer) { + WARN_ON_ONCE(1); return; + } if (buffer_pos == buffer_size) { atomic_inc(&oprofile_stats.event_lost_overflow); @@ -75,7 +80,6 @@ void wake_up_buffer_waiter(void) int alloc_event_buffer(void) { - int err = -ENOMEM; unsigned long flags; spin_lock_irqsave(&oprofilefs_lock, flags); @@ -86,13 +90,12 @@ int alloc_event_buffer(void) if (buffer_watershed >= buffer_size) return -EINVAL; + buffer_pos = 0; event_buffer = vmalloc(sizeof(unsigned long) * buffer_size); if (!event_buffer) - goto out; + return -ENOMEM; - err = 0; -out: - return err; + return 0; } @@ -100,6 +103,7 @@ void free_event_buffer(void) { mutex_lock(&buffer_mutex); vfree(event_buffer); + buffer_pos = 0; event_buffer = NULL; mutex_unlock(&buffer_mutex); } @@ -174,6 +178,7 @@ static ssize_t event_buffer_read(struct file *file, char __user *buf, mutex_lock(&buffer_mutex); + /* May happen if the buffer is freed during pending reads. */ if (!event_buffer) { retval = -EINTR; goto out; |