redonkable/remarkable-linux
redonkable/remarkable-linux
1
0
Fork 0
Code Releases Activity

ring-buffer: check for swapped buffers in start of committing

Browse source 
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>
This commit is contained in:
Steven Rostedt 2009-09-04 14:11:34 -04:00 committed by Steven Rostedt
parent e8165dbb03
commit 62f0b3eb5c
1 changed files with 17 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

20
kernel/trace/ring_buffer.c
View file

@ -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;