• Peter Zijlstra's avatar
    perf/core: Fix lock inversion between perf,trace,cpuhp · 82d94856
    Peter Zijlstra authored
    
    
    Lockdep gifted us with noticing the following 4-way lockup scenario:
    
            perf_trace_init()
     #0       mutex_lock(&event_mutex)
              perf_trace_event_init()
                perf_trace_event_reg()
                  tp_event->class->reg() := tracepoint_probe_register
     #1             mutex_lock(&tracepoints_mutex)
                      trace_point_add_func()
     #2                 static_key_enable()
    
     #2     do_cpu_up()
              perf_event_init_cpu()
     #3         mutex_lock(&pmus_lock)
     #4         mutex_lock(&ctx->mutex)
    
            perf_event_task_disable()
              mutex_lock(&current->perf_event_mutex)
     #4       ctx = perf_event_ctx_lock()
     #5       perf_event_for_each_child()
    
            do_exit()
              task_work_run()
                __fput()
                  perf_release()
                    perf_event_release_kernel()
     #4               mutex_lock(&ctx->mutex)
     #5               mutex_lock(&event->child_mutex)
                      free_event()
                        _free_event()
                          event->destroy() := perf_trace_destroy
     #0                     mutex_lock(&event_mutex);
    
    Fix that by moving the free_event() out from under the locks.
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vince Weaver <vincent.weaver@maine.edu>
    Cc: linux-kernel@vger.kernel.org
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    82d94856
core.c 265 KB