From e8d8a90fc5014e4cdcf1de2f320081d26c7f440f Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 18 Mar 2016 17:31:27 +0100 Subject: [PATCH] perf/x86/BTS: Fix RCU usage This splat reminds us: [ 8166.045595] [ INFO: suspicious RCU usage. ] [ 8166.168972] [] lockdep_rcu_suspicious+0xe7/0x120 [ 8166.175966] [] perf_callchain+0x23e/0x250 [ 8166.182280] [] perf_prepare_sample+0x27d/0x350 [ 8166.189082] [] intel_pmu_drain_bts_buffer+0x133/0x200 ... that as the core code does, one should hold rcu_read_lock() over that entire BTS event-output generation sequence as well. Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Andy Lutomirski Cc: Arnaldo Carvalho de Melo Cc: Borislav Petkov Cc: Brian Gerst Cc: David Ahern Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jiri Olsa Cc: Linus Torvalds Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Signed-off-by: Ingo Molnar --- arch/x86/events/intel/ds.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c index ce7211a07c0b..8584b90d8e0b 100644 --- a/arch/x86/events/intel/ds.c +++ b/arch/x86/events/intel/ds.c @@ -570,11 +570,12 @@ int intel_pmu_drain_bts_buffer(void) * We will overwrite the from and to address before we output * the sample. */ + rcu_read_lock(); perf_prepare_sample(&header, &data, event, ®s); if (perf_output_begin(&handle, event, header.size * (top - base - skip))) - return 1; + goto unlock; for (at = base; at < top; at++) { /* Filter out any records that contain kernel addresses. */ @@ -593,6 +594,8 @@ int intel_pmu_drain_bts_buffer(void) /* There's new data available. */ event->hw.interrupts++; event->pending_kill = POLL_IN; +unlock: + rcu_read_unlock(); return 1; } -- 2.30.2