diff options
| author |   Steven Rostedt <srostedt@redhat.com> | 2009-09-04 14:11:34 -0400 |
|---|---|---|
| committer |   Steven Rostedt <rostedt@goodmis.org> | 2009-09-04 19:38:42 -0400 |
| commit | 62f0b3eb5cb58931a02ee4e599e19c80a171e351 (patch) | |
| tree | 344b3b8f55e6162f7fa08316aa6fde333b304c04 /kernel/trace | |
| parent | tracing: report error in trace if we fail to swap latency buffer (diff) | |
| download | linux-dev-62f0b3eb5cb58931a02ee4e599e19c80a171e351.tar.xz linux-dev-62f0b3eb5cb58931a02ee4e599e19c80a171e351.zip | |
ring-buffer: check for swapped buffers in start of committing
Because the irqsoff tracer can swap an internal CPU buffer, it is possible
that a swap happens between the start of the write and before the committing
bit is set (the committing bit will disable swapping).
This patch adds a check for this and will fail the write if it detects it.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/ring_buffer.c | 20 |
1 files changed, 17 insertions, 3 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index f83a42a79ee8..1766c0e8db5a 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2073,7 +2073,8 @@ static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) } static struct ring_buffer_event * -rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer, +rb_reserve_next_event(struct ring_buffer *buffer, + struct ring_buffer_per_cpu *cpu_buffer, unsigned long length) { struct ring_buffer_event *event; @@ -2083,6 +2084,19 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer, rb_start_commit(cpu_buffer); + /* + * Due to the ability to swap a cpu buffer from a buffer + * it is possible it was swapped before we committed. + * (committing stops a swap). We check for it here and + * if it happened, we have to fail the write. + */ + barrier(); + if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) { + local_dec(&cpu_buffer->committing); + local_dec(&cpu_buffer->commits); + return NULL; + } + length = rb_calculate_event_length(length); again: /* @@ -2243,7 +2257,7 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) if (length > BUF_MAX_DATA_SIZE) goto out; - event = rb_reserve_next_event(cpu_buffer, length); + event = rb_reserve_next_event(buffer, cpu_buffer, length); if (!event) goto out; @@ -2476,7 +2490,7 @@ int ring_buffer_write(struct ring_buffer *buffer, if (length > BUF_MAX_DATA_SIZE) goto out; - event = rb_reserve_next_event(cpu_buffer, length); + event = rb_reserve_next_event(buffer, cpu_buffer, length); if (!event) goto out; |