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Subject[PATCH] coresight: trbe: Defer the probe on offline CPUs
Date
If a CPU is offline during the driver init, we could end up causing
a kernel crash trying to register the coresight device for the TRBE
instance.

e.g:

[ 0.149999] coresight ete0: CPU0: ete v1.1 initialized
[ 0.149999] coresight-etm4x ete_1: ETM arch init failed
[ 0.149999] coresight-etm4x: probe of ete_1 failed with error -22
[ 0.150085] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000050
[ 0.150085] Mem abort info:
[ 0.150085] ESR = 0x96000005
[ 0.150085] EC = 0x25: DABT (current EL), IL = 32 bits
[ 0.150085] SET = 0, FnV = 0
[ 0.150085] EA = 0, S1PTW = 0
[ 0.150085] Data abort info:
[ 0.150085] ISV = 0, ISS = 0x00000005
[ 0.150085] CM = 0, WnR = 0
[ 0.150085] [0000000000000050] user address but active_mm is swapper
[ 0.150085] Internal error: Oops: 96000005 [#1] PREEMPT SMP
[ 0.150085] Modules linked in:
[ 0.150085] Hardware name: FVP Base RevC (DT)
[ 0.150085] pstate: 00800009 (nzcv daif -PAN +UAO -TCO BTYPE=--)
[ 0.150155] pc : arm_trbe_register_coresight_cpu+0x74/0x144
[ 0.150155] lr : arm_trbe_register_coresight_cpu+0x48/0x144
...

[ 0.150237] Call trace:
[ 0.150237] arm_trbe_register_coresight_cpu+0x74/0x144
[ 0.150237] arm_trbe_device_probe+0x1c0/0x2d8
[ 0.150259] platform_drv_probe+0x94/0xbc
[ 0.150259] really_probe+0x1bc/0x4a8
[ 0.150266] driver_probe_device+0x7c/0xb8
[ 0.150266] device_driver_attach+0x6c/0xac
[ 0.150266] __driver_attach+0xc4/0x148
[ 0.150266] bus_for_each_dev+0x7c/0xc8
[ 0.150266] driver_attach+0x24/0x30
[ 0.150266] bus_add_driver+0x100/0x1e0
[ 0.150266] driver_register+0x78/0x110
[ 0.150266] __platform_driver_register+0x44/0x50
[ 0.150266] arm_trbe_init+0x28/0x84
[ 0.150266] do_one_initcall+0x94/0x2bc
[ 0.150266] do_initcall_level+0xa4/0x158
[ 0.150266] do_initcalls+0x54/0x94
[ 0.150319] do_basic_setup+0x24/0x30
[ 0.150319] kernel_init_freeable+0xe8/0x14c
[ 0.150319] kernel_init+0x14/0x18c
[ 0.150319] ret_from_fork+0x10/0x30
[ 0.150319] Code: f94012c8 b0004ce2 9134a442 52819801 (f9402917)
[ 0.150319] ---[ end trace d23e0cfe5098535e ]---
[ 0.150346] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b

Fix this by skipping the step, if we are unable to probe the CPU.

Fixes: 3fbf7f011f24 ("coresight: sink: Add TRBE driver")
Reported-by: Bransilav Rankov <branislav.rankov@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Leo Yan <leo.yan@linaro.org>
Tested-by: Branislav Rankov <branislav.rankov@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
drivers/hwtracing/coresight/coresight-trbe.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index 5d350acef798..85ceda68af82 100644
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -1286,7 +1286,9 @@ static int arm_trbe_probe_coresight(struct trbe_drvdata *drvdata)
return -ENOMEM;

for_each_cpu(cpu, &drvdata->supported_cpus) {
- smp_call_function_single(cpu, arm_trbe_probe_cpu, drvdata, 1);
+ /* If we fail to probe the CPU, let us defer it to hotplug callbacks */
+ if (smp_call_function_single(cpu, arm_trbe_probe_cpu, drvdata, 1))
+ continue;
if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
arm_trbe_register_coresight_cpu(drvdata, cpu);
if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
--
2.25.4
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