On Wed, 15 Oct 2014, Vince Weaver wrote: > I can use sysrq to get the stack trace, the one CPU is stuck in a call > to find_get_context(). > > An example backtrace: > > [88200.300003] <EOI> > [88200.300003] [<ffffffff81114869>] ? ____cache_alloc+0x130/0x25b > [88200.300003] [<ffffffff8107fb05>] ? __call_rcu.constprop.63+0x1bf/0x1cb > [88200.300003] [<ffffffff8107fb2b>] kfree_call_rcu+0x1a/0x1c > [88200.300003] [<ffffffff810cf84f>] put_ctx+0x51/0x55 > [88200.300003] [<ffffffff810d1840>] find_get_context+0x166/0x195 > [88200.300003] [<ffffffff810d5856>] SYSC_perf_event_open+0x47b/0x7f5 > [88200.300003] [<ffffffff810d5f55>] SyS_perf_event_open+0xe/0x10 > [88200.300003] [<ffffffff815362d6>] system_call_fastpath+0x16/0x1b > > It looks like the > else if (task->perf_event_ctxp[ctxn]) > err = -EAGAIN;
It is indeed stuck there, waiting for task->perf_event_ctxp[1] to get set to zero, which never happens. As far as I can tell it's when a Software event is being opened. Still struggling through the code trying to figure out what's going on. [ 7071.252607] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7071.259439] VMW: type=1 config=8 [ 7071.262713] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7071.269506] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7071.276299] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7071.283087] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7071.289879] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7071.296671] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7071.303457] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7071.310248] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7071.317035] VMW: task->perf_event_ctxp[1]=ffff8800cb12ec00, EAGAIN, ref=1 [ 7076.256032] find_get_context: 7246310 callbacks suppressed Vince -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
