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tracing: fix mmiotrace resizing crash

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Pekka reported a crash when resizing the mmiotrace tracer (if only
mmiotrace is enabled).

This happens because in that case we do not allocate the max buffer,
but we try to use it.

Make ring_buffer_resize() idempotent against NULL buffers.

Reported-by: Pekka Paalanen <pq@iki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2008-11-13 14:58:31 +01:00
parent 47e74f2ba8
commit ee51a1de7e
1 changed files with 6 additions and 0 deletions
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6
kernel/trace/ring_buffer.c
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@ -538,6 +538,12 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
LIST_HEAD(pages); LIST_HEAD(pages);
int i, cpu; int i, cpu;
/*
* Always succeed at resizing a non-existent buffer:
*/
if (!buffer)
return size;
size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
size *= BUF_PAGE_SIZE; size *= BUF_PAGE_SIZE;
buffer_size = buffer->pages * BUF_PAGE_SIZE; buffer_size = buffer->pages * BUF_PAGE_SIZE;