From 0c99241c93b8060441f3c8434848e54b5338f922 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Thu, 16 Apr 2015 12:38:30 +0200 Subject: [PATCH] perf/x86/intel/pt: Fix and clean up error handling in pt_event_add() Dan Carpenter reported that pt_event_add() has buggy error handling logic: it returns 0 instead of -EBUSY when it fails to start a newly added event. Furthermore, the control flow in this function is messy, with cleanup labels mixed with direct returns. Fix the bug and clean up the code by converting it to a straight fast path for the regular non-failing case, plus a clear sequence of cascading goto labels to do all cleanup. NOTE: I materially changed the existing clean up logic in the pt_event_start() failure case to use the direct perf_aux_output_end() path, not pt_event_del(), because perf_aux_output_end() is enough here. Reported-by: Dan Carpenter Acked-by: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Julia Lawall Cc: Linus Torvalds Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20150416103830.GB7847@gmail.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_intel_pt.c | 33 ++++++++++++++----------------- 1 file changed, 15 insertions(+), 18 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c index f277064..ffe666c 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_pt.c +++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c @@ -988,39 +988,36 @@ static int pt_event_add(struct perf_event *event, int mode) int ret = -EBUSY; if (pt->handle.event) - goto out; + goto fail; buf = perf_aux_output_begin(&pt->handle, event); - if (!buf) { - ret = -EINVAL; - goto out; - } + ret = -EINVAL; + if (!buf) + goto fail_stop; pt_buffer_reset_offsets(buf, pt->handle.head); if (!buf->snapshot) { ret = pt_buffer_reset_markers(buf, &pt->handle); - if (ret) { - perf_aux_output_end(&pt->handle, 0, true); - goto out; - } + if (ret) + goto fail_end_stop; } if (mode & PERF_EF_START) { pt_event_start(event, 0); - if (hwc->state == PERF_HES_STOPPED) { - pt_event_del(event, 0); - ret = -EBUSY; - } + ret = -EBUSY; + if (hwc->state == PERF_HES_STOPPED) + goto fail_end_stop; } else { hwc->state = PERF_HES_STOPPED; } - ret = 0; -out: - - if (ret) - hwc->state = PERF_HES_STOPPED; + return 0; +fail_end_stop: + perf_aux_output_end(&pt->handle, 0, true); +fail_stop: + hwc->state = PERF_HES_STOPPED; +fail: return ret; } -- 2.7.4