linux-kernel - 4.7-rc1/s390: WARNING: CPU: 5 PID: 1 at kernel/events/core.c:8485 perf_pmu

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Date:	Mon, 6 Jun 2016 09:37:41 +0200
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-s390 <linux-s390@...r.kernel.org>,
	"linux-kernel@...r.kernel.org >> Linux Kernel Mailing List" 
	<linux-kernel@...r.kernel.org>
Subject: 4.7-rc1/s390: WARNING: CPU: 5 PID: 1 at kernel/events/core.c:8485
 perf_pmu_register+0x420/0x428

Peter, Hendrik,

commit 26657848502b ("perf/core: Verify we have a single perf_hw_context PMU") seems to 
trigger the newly created warning on a z196.


[    2.202363] ------------[ cut here ]------------
[    2.202372] WARNING: CPU: 5 PID: 1 at kernel/events/core.c:8485 perf_pmu_register+0x420/0x428
[    2.202373] Modules linked in:
[    2.202377] CPU: 5 PID: 1 Comm: swapper/0 Not tainted 4.7.0-rc1+ #2
[    2.202379] task: 00000009c5240000 ti: 00000009c5234000 task.ti: 00000009c5234000
[    2.202381] Krnl PSW : 0704c00180000000 0000000000220c50 (perf_pmu_register+0x420/0x428)
[    2.202385]            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
Krnl GPRS: ffffffffffffffff 0000000000b15ac6 0000000000000000 00000009cb440000
[    2.202388]            000000000022087a 0000000000000000 0000000000b78fa0 0000000000000000
[    2.202390]            0000000000a9aa90 0000000000000084 0000000000000005 000000000088a97a
[    2.202405]            0000000000000004 0000000000749dd0 000000000022087a 00000009c5237cc0
[    2.202415] Krnl Code: 0000000000220c44: a7f4ff54            brc     15,220aec
           0000000000220c48: 92011000           mvi     0(%r1),1
          #0000000000220c4c: a7f40001           brc     15,220c4e
          >0000000000220c50: a7f4ff12           brc     15,220a74
           0000000000220c54: 0707               bcr     0,%r7
           0000000000220c56: 0707               bcr     0,%r7
           0000000000220c58: ebdff0800024       stmg    %r13,%r15,128(%r15)
           0000000000220c5e: a7f13fe0           tmll    %r15,16352
[    2.202431] Call Trace:
[    2.202433] ([<000000000022087a>] perf_pmu_register+0x4a/0x428)
[    2.202438] ([<0000000000b2c25c>] init_cpum_sampling_pmu+0x14c/0x1f8)
[    2.202441] ([<0000000000100248>] do_one_initcall+0x48/0x140)
[    2.202444] ([<0000000000b25d26>] kernel_init_freeable+0x1e6/0x2a0)
[    2.202449] ([<000000000072bda4>] kernel_init+0x24/0x138)
[    2.202453] ([<000000000073495e>] kernel_thread_starter+0x6/0xc)
[    2.202455] ([<0000000000734958>] kernel_thread_starter+0x0/0xc)
[    2.202456] Last Breaking-Event-Address:
[    2.202458]  [<0000000000220c4c>] perf_pmu_register+0x41c/0x428
[    2.202460] ---[ end trace 0c6ef9f5b771ad97 ]---

Looks like perf_pmu_register does not like to be called twice (once for the counter
and once for the sampling facility).

Christian