From 1ff3d7d79204612ebe2e611d2592f8898908ca00 Mon Sep 17 00:00:00 2001 From: Cyrill Gorcunov Date: Fri, 14 May 2010 23:08:15 +0400 Subject: [PATCH] x86, perf: P4 PMU - fix counters management logic Jaswinder reported this #GP: | | Message from syslogd@ht at May 14 09:39:32 ... | kernel:[ 314.908612] EIP: [] | x86_perf_event_set_period+0x19d/0x1b2 SS:ESP 0068:edac3d70 | Ming has narrowed it down to a comparision issue between arguments with different sizes and signs. As result event index reached a wrong value which in turn led to a GP fault. At the same time it was found that p4_next_cntr has broken logic and should return the counter index only if it was not yet borrowed for another event. Reported-by: Jaswinder Singh Rajput Reported-by: Lin Ming Bisected-by: Lin Ming Tested-by: Jaswinder Singh Rajput Signed-off-by: Cyrill Gorcunov CC: Peter Zijlstra CC: Frederic Weisbecker LKML-Reference: <20100514190815.GG13509@lenovo> Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_p4.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c index cb875b1e2e8..424fc8de68e 100644 --- a/arch/x86/kernel/cpu/perf_event_p4.c +++ b/arch/x86/kernel/cpu/perf_event_p4.c @@ -18,7 +18,7 @@ struct p4_event_bind { unsigned int opcode; /* Event code and ESCR selector */ unsigned int escr_msr[2]; /* ESCR MSR for this event */ - unsigned char cntr[2][P4_CNTR_LIMIT]; /* counter index (offset), -1 on abscence */ + char cntr[2][P4_CNTR_LIMIT]; /* counter index (offset), -1 on abscence */ }; struct p4_cache_event_bind { @@ -747,11 +747,11 @@ static int p4_get_escr_idx(unsigned int addr) static int p4_next_cntr(int thread, unsigned long *used_mask, struct p4_event_bind *bind) { - int i = 0, j; + int i, j; for (i = 0; i < P4_CNTR_LIMIT; i++) { - j = bind->cntr[thread][i++]; - if (j == -1 || !test_bit(j, used_mask)) + j = bind->cntr[thread][i]; + if (j != -1 && !test_bit(j, used_mask)) return j; } -- 2.39.3