If the specified/hinted sink is not reachable from a subset of the CPUs,
we could end up unable to trace the event on those CPUs. This
is the best effort we could do until we support 1:1 configurations.
Fail gracefully in such cases avoiding a WARN_ON, which can be easily
triggered by the user on certain platforms (Arm N1SDP), with the following
trace paths :
CPU0
\
-- Funnel0 --> ETF0 -->
/ \
CPU1 \
MainFunnel
CPU2 /
\ /
-- Funnel1 --> ETF1 -->
/
CPU1
$ perf record --per-thread -e cs_etm/@ETF0/u -- <app>
could trigger the following WARNING, when the event is scheduled
on CPU2.
[10919.513250] ------------[ cut here ]------------
[10919.517861] WARNING: CPU: 2 PID: 24021 at
drivers/hwtracing/coresight/coresight-etm-perf.c:316 etm_event_start+0xf8/0x100
...
[10919.564403] CPU: 2 PID: 24021 Comm: perf Not tainted 5.8.0+ #24
[10919.570308] pstate:
80400089 (Nzcv daIf +PAN -UAO BTYPE=--)
[10919.575865] pc : etm_event_start+0xf8/0x100
[10919.580034] lr : etm_event_start+0x80/0x100
[10919.584202] sp :
fffffe001932f940
[10919.587502] x29:
fffffe001932f940 x28:
fffffc834995f800
[10919.592799] x27:
0000000000000000 x26:
fffffe0011f3ced0
[10919.598095] x25:
fffffc837fce244c x24:
fffffc837fce2448
[10919.603391] x23:
0000000000000002 x22:
fffffc8353529c00
[10919.608688] x21:
fffffc835bb31000 x20:
0000000000000000
[10919.613984] x19:
fffffc837fcdcc70 x18:
0000000000000000
[10919.619281] x17:
0000000000000000 x16:
0000000000000000
[10919.624577] x15:
0000000000000000 x14:
00000000000009f8
[10919.629874] x13:
00000000000009f8 x12:
0000000000000018
[10919.635170] x11:
0000000000000000 x10:
0000000000000000
[10919.640467] x9 :
fffffe00108cd168 x8 :
0000000000000000
[10919.645763] x7 :
0000000000000020 x6 :
0000000000000001
[10919.651059] x5 :
0000000000000002 x4 :
0000000000000001
[10919.656356] x3 :
0000000000000000 x2 :
0000000000000000
[10919.661652] x1 :
fffffe836eb40000 x0 :
0000000000000000
[10919.666949] Call trace:
[10919.669382] etm_event_start+0xf8/0x100
[10919.673203] etm_event_add+0x40/0x60
[10919.676765] event_sched_in.isra.134+0xcc/0x210
[10919.681281] merge_sched_in+0xb0/0x2a8
[10919.685017] visit_groups_merge.constprop.140+0x15c/0x4b8
[10919.690400] ctx_sched_in+0x15c/0x170
[10919.694048] perf_event_sched_in+0x6c/0xa0
[10919.698130] ctx_resched+0x60/0xa0
[10919.701517] perf_event_exec+0x288/0x2f0
[10919.705425] begin_new_exec+0x4c8/0xf58
[10919.709247] load_elf_binary+0x66c/0xf30
[10919.713155] exec_binprm+0x15c/0x450
[10919.716716] __do_execve_file+0x508/0x748
[10919.720711] __arm64_sys_execve+0x40/0x50
[10919.724707] do_el0_svc+0xf4/0x1b8
[10919.728095] el0_sync_handler+0xf8/0x124
[10919.732003] el0_sync+0x140/0x180
Even though we don't support using separate sinks for the ETMs yet (e.g,
for 1:1 configurations), we should at least honor the user's choice and
handle the limitations gracefully, by simply skipping the tracing on ETMs
which can't reach the requested sink.
Fixes:
f9d81a657bb8 ("coresight: perf: Allow tracing on hotplugged CPUs")
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Reported-by: Jeremy Linton <jeremy.linton@arm.com>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200916191737.4001561-11-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>