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Date: Tue, 5 Dec 2017 11:00:38 +0530
From: Anju T Sudhakar <anju@...ux.vnet.ibm.com>
To: mpe@...erman.id.au
Cc: linuxppc-dev@...ts.ozlabs.org, maddy@...ux.vnet.ibm.com,
anju@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org
Subject: [PATCH] powerpc/perf: Fix nest-imc cpuhotplug callback failure
Call trace observed during boot:
Faulting instruction address: 0xc000000000248340
cpu 0x0: Vector: 380 (Data Access Out of Range) at [c000000ff66fb850]
pc: c000000000248340: event_function_call+0x50/0x1f0
lr: c00000000024878c: perf_remove_from_context+0x3c/0x100
sp: c000000ff66fbad0
msr: 9000000000009033
dar: 7d20e2a6f92d03c0
current = 0xc000000ff6679200
paca = 0xc00000000fd40000 softe: 0 irq_happened: 0x01
pid = 14, comm = cpuhp/0
Linux version 4.14.0-rc2-42789-ge8eae4b (rgrimm@...X) (gcc version 5.4.0
20160609 (Ubuntu/IBM 5.4.0-6ubuntu1~16.04.4)) #1 SMP Thu Nov 16 14:35:14 CST
2017
enter ? for help
[c000000ff66fbb80] c00000000024878c perf_remove_from_context+0x3c/0x100
[c000000ff66fbbc0] c00000000024e84c perf_pmu_migrate_context+0x10c/0x380
[c000000ff66fbc60] c0000000000ca050 ppc_nest_imc_cpu_offline+0x1b0/0x210
[c000000ff66fbcb0] c0000000000d5d54 cpuhp_invoke_callback+0x194/0x620
[c000000ff66fbd20] c0000000000d702c cpuhp_thread_fun+0x7c/0x1b0
[c000000ff66fbd60] c00000000010ad90 smpboot_thread_fn+0x290/0x2a0
[c000000ff66fbdc0] c000000000104818 kthread+0x168/0x1b0
[c000000ff66fbe30] c00000000000b5a0 ret_from_kernel_thread+0x5c/0xbc
While registering the cpuhotplug callbacks for nest-imc, if we fail in the
cpuhotplug online path for any random node in a multi node system (because
the opal call to stop nest-imc counters fails for that node),
ppc_nest_imc_cpu_offline() will get invoked for other nodes who successfully
returned from cpuhotplug online path.
This call trace is generated since in the ppc_nest_imc_cpu_offline()
path we are trying to migrate the event context, when nest-imc counters are
not even initialized.
Patch to add a check to ensure that nest-imc is registered before migrating
the event context.
Note:
Madhavan Srinivasan has recently send a skiboot patch to have a check in the
skiboot code to make sure that the microcode is initialized in all the chips,
before enabling the nest units.
https://patchwork.ozlabs.org/patch/844047/ (v2)
Signed-off-by: Anju T Sudhakar <anju@...ux.vnet.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
---
arch/powerpc/perf/imc-pmu.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
index 0ead3cd..9daa1c3 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -309,6 +309,20 @@ static int ppc_nest_imc_cpu_offline(unsigned int cpu)
if (!cpumask_test_and_clear_cpu(cpu, &nest_imc_cpumask))
return 0;
+ /*
+ * Check whether nest_imc is registered. We could end up here
+ * if the cpuhotplug callback registration fails. i.e, callback
+ * invokes the offline path for all successfully registered nodes.
+ * At this stage, nest_imc pmu will not be registered and we
+ * should return here.
+ *
+ * We return with a zero since this is not an offline failure.
+ * And cpuhp_setup_state() returns the actual failure reason
+ * to the caller, which inturn will call the cleanup routine.
+ */
+ if (!nest_pmus)
+ return 0;
+
/*
* Now that this cpu is one of the designated,
* find a next cpu a) which is online and b) in same chip.
--
2.7.4
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