Re: powerpc/perf: Remove sched_task function defined for thread-imc

On Fri, 2018-05-18 at 07:35:25 UTC, Anju T Sudhakar wrote:

Call trace observed while running perf-fuzzer:

[  329.228068] CPU: 43 PID: 9088 Comm: perf_fuzzer Not tainted 4.13.0-32-generic #35~lp1746225
[  329.228070] task: c000003f776ac900 task.stack: c000003f77728000
[  329.228071] NIP: c000000000299b70 LR: c0000000002a4534 CTR: c00000000029bb80
[  329.228073] REGS: c000003f7772b760 TRAP: 0700   Not tainted  (4.13.0-32-generic)
[  329.228073] MSR: 900000000282b033 <SF,HV,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>
[  329.228079]   CR: 24008822  XER: 00000000
[  329.228080] CFAR: c000000000299a70 SOFTE: 0
GPR00: c0000000002a4534 c000003f7772b9e0 c000000001606200 c000003fef858908
GPR04: c000003f776ac900 0000000000000001 ffffffffffffffff 0000003fee730000
GPR08: 0000000000000000 0000000000000000 c0000000011220d8 0000000000000002
GPR12: c00000000029bb80 c000000007a3d900 0000000000000000 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: 0000000000000000 0000000000000000 c000003f776ad090 c000000000c71354
GPR24: c000003fef716780 0000003fee730000 c000003fe69d4200 c000003f776ad330
GPR28: c0000000011220d8 0000000000000001 c0000000014c6108 c000003fef858900
[  329.228098] NIP [c000000000299b70] perf_pmu_sched_task+0x170/0x180
[  329.228100] LR [c0000000002a4534] __perf_event_task_sched_in+0xc4/0x230
[  329.228101] Call Trace:
[  329.228102] [c000003f7772b9e0] [c0000000002a0678] perf_iterate_sb+0x158/0x2a0 (unreliable)
[  329.228105] [c000003f7772ba30] [c0000000002a4534] __perf_event_task_sched_in+0xc4/0x230
[  329.228107] [c000003f7772bab0] [c0000000001396dc] finish_task_switch+0x21c/0x310
[  329.228109] [c000003f7772bb60] [c000000000c71354] __schedule+0x304/0xb80
[  329.228111] [c000003f7772bc40] [c000000000c71c10] schedule+0x40/0xc0
[  329.228113] [c000003f7772bc60] [c0000000001033f4] do_wait+0x254/0x2e0
[  329.228115] [c000003f7772bcd0] [c000000000104ac0] kernel_wait4+0xa0/0x1a0
[  329.228117] [c000003f7772bd70] [c000000000104c24] SyS_wait4+0x64/0xc0
[  329.228121] [c000003f7772be30] [c00000000000b184] system_call+0x58/0x6c
[  329.228121] Instruction dump:
[  329.228123] 3beafea0 7faa4800 409eff18 e8010060 eb610028 ebc10040 7c0803a6 38210050
[  329.228127] eb81ffe0 eba1ffe8 ebe1fff8 4e800020 <0fe00000> 4bffffbc 60000000 60420000
[  329.228131] ---[ end trace 8c46856d314c1811 ]---
[  375.755943] hrtimer: interrupt took 31601 ns


The context switch call-backs for thread-imc are defined in sched_task function.
So when thread-imc events are grouped with software pmu events,
perf_pmu_sched_task hits the WARN_ON_ONCE condition, since software PMUs are
assumed not to have a sched_task defined. 
 
Patch to move the thread_imc enable/disable opal call back from sched_task to
event_[add/del] function

Signed-off-by: Anju T Sudhakar <redacted>
Reviewed-by: Madhavan Srinivasan <redacted>
Tested-by: Joel Stanley <joel@jms.id.au>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/7ccc4fe5ff9e3a134e863beed0dba1

cheers