path: root/mm
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authorSteven Rostedt <srostedt@redhat.com>2009-03-30 14:03:19 -0400
committerIngo Molnar <mingo@elte.hu>2009-04-01 14:47:53 +0200
commit2e572895bf3203e881356a4039ab0fa428ed2639 (patch)
tree8b49b2b7ea1f1a9ec31e82a999d7c257978f33ff /mm
parentfunction-graph: allow unregistering twice (diff)
ring-buffer: do not remove reader page from list on ring buffer free
Impact: prevent possible memory leak The reader page of the ring buffer is special. Although it points into the ring buffer, it is not part of the actual buffer. It is a page used by the reader to swap with a page in the ring buffer. Once the swap is made, the new reader page is again outside the buffer. Even though the reader page points into the buffer, it is really pointing to residual data. Note, this data is used by the reader. reader page | v (prev) +---+ (next) +----------| |----------+ | +---+ | v v +---+ +---+ +---+ -->| |------->| |------->| |---> <--| |<-------| |<-------| |<--- +---+ +---+ +---+ ^ ^ ^ \ | / ------- Buffer--------- If we perform a list_del_init() on the reader page we will actually remove the last page the reader swapped with and not the reader page itself. This will cause that page to not be freed, and thus is a memory leak. Luckily, the only user of the ring buffer so far is ftrace. And ftrace will not free its ring buffer after it allocates it. There is no current possible memory leak. But once there are other users, or if ftrace dynamically creates and frees its ring buffer, then this would be a memory leak. This patch fixes the leak for future cases. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'mm')
0 files changed, 0 insertions, 0 deletions