1. 10 Jul, 2023 1 commit
    • Namhyung Kim's avatar
      perf/x86: Fix lockdep warning in for_each_sibling_event() on SPR · 27c68c21
      Namhyung Kim authored
      On SPR, the load latency event needs an auxiliary event in the same
      group to work properly.  There's a check in intel_pmu_hw_config()
      for this to iterate sibling events and find a mem-loads-aux event.
      
      The for_each_sibling_event() has a lockdep assert to make sure if it
      disabled hardirq or hold leader->ctx->mutex.  This works well if the
      given event has a separate leader event since perf_try_init_event()
      grabs the leader->ctx->mutex to protect the sibling list.  But it can
      cause a problem when the event itself is a leader since the event is
      not initialized yet and there's no ctx for the event.
      
      Actually I got a lockdep warning when I run the below command on SPR,
      but I guess it could be a NULL pointer dereference.
      
        $ perf record -d -e cpu/mem-loads/uP true
      
      The code path to the warning is:
      
        sys_perf_event_open()
          perf_event_alloc()
            perf_init_event()
              perf_try_init_event()
                x86_pmu_event_init()
                  hsw_hw_config()
                    intel_pmu_hw_config()
                      for_each_sibling_event()
                        lockdep_assert_event_ctx()
      
      We don't need for_each_sibling_event() when it's a standalone event.
      Let's return the error code directly.
      
      Fixes: f3c0eba2 ("perf: Add a few assertions")
      Reported-by: default avatarGreg Thelen <gthelen@google.com>
      Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
      Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: stable@vger.kernel.org
      Link: https://lkml.kernel.org/r/20230704181516.3293665-1-namhyung@kernel.org
      27c68c21
  2. 09 Jul, 2023 10 commits
  3. 08 Jul, 2023 29 commits