Messages in this thread Patch in this message | | | Date | Mon, 26 Jan 2004 02:37:15 +0000 | From | Philippe Elie <> | Subject | [PATCH] oprofile per-cpu buffer overrun |
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Hi Andrew,
In a ring buffer controlled by a read and write positions we can't use buffer_size but only buffer_size - 1 entry, the last free entry act as a guard to avoid write pos overrun. This bug was hidden because the writer, oprofile_add_sample(), request one more entry than really needed.
regards, Phil
Index: drivers/oprofile/cpu_buffer.c =================================================================== RCS file: /usr/local/cvsroot/linux-2.5/drivers/oprofile/cpu_buffer.c,v retrieving revision 1.9 diff -u -p -r1.9 cpu_buffer.c --- drivers/oprofile/cpu_buffer.c 26 May 2003 04:42:54 -0000 1.9 +++ drivers/oprofile/cpu_buffer.c 24 Jan 2004 21:07:03 -0000 @@ -86,9 +86,9 @@ static unsigned long nr_available_slots( unsigned long tail = b->tail_pos; if (tail > head) - return tail - head; + return (tail - head) - 1; - return tail + (b->buffer_size - head); + return tail + (b->buffer_size - head) - 1; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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