• Peter Zijlstra's avatar
    perf: Fix irq_work 'tail' recursion · a49a0c95
    Peter Zijlstra authored
    commit d525211f9d1be8b523ec7633f080f2116f5ea536 upstream.
    
    Vince reported a watchdog lockup like:
    
    	[<ffffffff8115e114>] perf_tp_event+0xc4/0x210
    	[<ffffffff810b4f8a>] perf_trace_lock+0x12a/0x160
    	[<ffffffff810b7f10>] lock_release+0x130/0x260
    	[<ffffffff816c7474>] _raw_spin_unlock_irqrestore+0x24/0x40
    	[<ffffffff8107bb4d>] do_send_sig_info+0x5d/0x80
    	[<ffffffff811f69df>] send_sigio_to_task+0x12f/0x1a0
    	[<ffffffff811f71ce>] send_sigio+0xae/0x100
    	[<ffffffff811f72b7>] kill_fasync+0x97/0xf0
    	[<ffffffff8115d0b4>] perf_event_wakeup+0xd4/0xf0
    	[<ffffffff8115d103>] perf_pending_event+0x33/0x60
    	[<ffffffff8114e3fc>] irq_work_run_list+0x4c/0x80
    	[<ffffffff8114e448>] irq_work_run+0x18/0x40
    	[<ffffffff810196af>] smp_trace_irq_work_interrupt+0x3f/0xc0
    	[<ffffffff816c99bd>] trace_irq_work_interrupt+0x6d/0x80
    
    Which is caused by an irq_work generating new irq_work and therefore
    not allowing forward progress.
    
    This happens because processing the perf irq_work triggers another
    perf event (tracepoint stuff) which in turn generates an irq_work ad
    infinitum.
    
    Avoid this by raising the recursion counter in the irq_work -- which
    effectively disables all software events (including tracepoints) from
    actually triggering again.
    Reported-by: 's avatarVince Weaver <vincent.weaver@maine.edu>
    Tested-by: 's avatarVince Weaver <vincent.weaver@maine.edu>
    Signed-off-by: 's avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Link: http://lkml.kernel.org/r/20150219170311.GH21418@twins.programming.kicks-ass.netSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    a49a0c95
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