Re: perf_callchain_user oops

[Dave Jones]

On Thu, Mar 23, 2017 at 10:40:22AM +0100, Peter Zijlstra wrote:
 > On Wed, Mar 22, 2017 at 10:58:04PM -0400, Dave Jones wrote:
 > > Not seen this one before..
 > > 
 > > Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC
 > 
 > That's a write fault reaching no_context() afaict.
 > 
 > > CPU: 1 PID: 24420 Comm: trinity-main Not tainted 4.11.0-rc3-think+ #3 
 > > task: ffff8804f4c85440 task.stack: ffffc90001d38000
 > > RIP: 0010:perf_callchain_user+0x11e/0x220
 > > RSP: 0000:ffffc90001d3ba98 EFLAGS: 00010246
 > > RAX: ffff88044c59c2a8 RBX: ffffc90001d3bae8 RCX: 0000562bce3f6e40
 > > RDX: 0000562bce3f6e40 RSI: 00007fffffffeff0 RDI: 0000000000000000
 > > RBP: ffffc90001d3bab8 R08: 00000000bffffff0 R09: 00000000ffffdff0
 > > R10: 0000000000002faa R11: 0000000000002fab R12: ffff8804f4c85440
 > > R13: ffffc90001d3bf58 R14: ffffc90001d3bf58 R15: 0000000000000000
 > > FS:  00007f34b3969b40(0000) GS:ffff880507a00000(0000) knlGS:0000000000000000
 > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 > > CR2: ffff88044c5b4000 CR3: 000000044c584000 CR4: 00000000001406e0
 > > DR0: 00007f34b382e000 DR1: 0000000000000000 DR2: 0000000000000000
 > > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
 > > Call Trace:
 > >  get_perf_callchain+0x258/0x2b0
 > >  perf_callchain+0x79/0x80
 > >  perf_prepare_sample+0x27e/0x360
 > >  perf_event_output_forward+0x75/0x160
 > 
 > Any chance you could run scripts/faddr2line on this output?
 > 
 > I cannot seem to match the Code with a defconfig build of that function.

$ scripts/faddr2line arch/x86/events/core.o  perf_callchain_user+0x11e 
perf_callchain_user+0x11e/0x220:
perf_callchain_store at include/linux/perf_event.h:1148
 (inlined by) perf_callchain_user at arch/x86/events/core.c:2444

$ scripts/faddr2line kernel/events/callchain.o get_perf_callchain+0x258/0x2b0 perf_callchain+0x79/0x80 
get_perf_callchain+0x258/0x2b0:
get_perf_callchain at kernel/events/callchain.c:237

perf_callchain+0x79/0x80:
perf_callchain at kernel/events/callchain.c:194

$ scripts/faddr2line kernel/events/core.o perf_prepare_sample+0x27e/0x360
perf_prepare_sample+0x27e/0x360:
perf_prepare_sample at kernel/events/core.c:5991

$ scripts/faddr2line kernel/events/core.o perf_event_output_forward+0x75/0x160
perf_event_output_forward+0x75/0x160:
__perf_event_output at kernel/events/core.c:6104
 (inlined by) perf_event_output_forward at kernel/events/core.c:6120