Re: [PATCH] coresight: etm_perf: Fix using uninitialised work

[Mike Leach]

Tested against the 4.11-rc1 OpenCSD perf tree - reproduced the problem
and confirmed the patch fixes it on Juno r1.
Noted that the command line
./perf record -e cs_etm/@20010000.etf/ uname
also causes the same problem,

Larger question that may need future investigation in the openCSD
project is why the sink provided in the perf command line is not being
enabled?

Regards

Mike

On 31 March 2017 at 19:18, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
> With 4.11-rc4, the following command triggers a WARN_ON,
> when a sink is not enabled.
>
>  perf record -e cs_etm/@20010000.etf/
>
>  [88286.547741] ------------[ cut here ]------------
>  [88286.552332] WARNING: CPU: 3 PID: 2156 at kernel/workqueue.c:1442 __queue_work+0x29c/0x3b8
>  [88286.560427] Modules linked in:
>  [88286.563451]
>  [88286.564928] CPU: 3 PID: 2156 Comm: perf_v4.11 Not tainted 4.11.0-rc4 #217
>  [88286.573453] Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform, BIOS EDK II Aug 15
>   2016
>  [88286.584128] task: ffff80097597c200 task.stack: ffff8009768b0000
>  [88286.589990] PC is at __queue_work+0x29c/0x3b8
>  [88286.594303] LR is at __queue_work+0x104/0x3b8
>  [88286.598614] pc : [<ffff0000080d8c7c>] lr : [<ffff0000080d8ae4>] pstate: a00001c5
>  [88286.605934] sp : ffff8009768b3aa0
>  [88286.609212] x29: ffff8009768b3aa0 x28: ffff80097ff3da00
>  [88286.614477] x27: ffff80097ff89c00 x26: ffff8009751b0e00
>  [88286.619741] x25: ffff000008c9f000 x24: 0000000000000003
>  [88286.625004] x23: 0000000000000040 x22: ffff000008d3dab8
>  [88286.630268] x21: ffff800977804400 x20: 0000000000000007
>  [88286.635532] x19: ffff000008c54000 x18: 0000fffff9185160
>  [88286.640795] x17: 0000ffffb33d9a38 x16: ffff000008088270
>  [88286.646059] x15: 0000ffffb345b590 x14: 0000000000000000
>  [88286.651322] x13: 0000000000000004 x12: 0000000000000040
>  [88286.656586] x11: 0000000000000068 x10: 0000000000000000
>  [88286.661849] x9 : ffff800977400028 x8 : 0000000000000000
>  [88286.667113] x7 : 0000000000000000 x6 : ffff0000080d8ae4
>  [88286.672376] x5 : 0000000000000000 x4 : 0000000000000080
>  [88286.677639] x3 : 0000000000000000 x2 : 0000000000000000
>  [88286.682903] x1 : 0000000000000000 x0 : ffff8009751b0e08
>  [88286.688166]
>  [88286.689638] ---[ end trace 31633f18fd33d4cb ]---
>  [88286.694206] Call trace:
>  [88286.696627] Exception stack(0xffff8009768b38d0 to 0xffff8009768b3a00)
>  [88286.703004] 38c0:                                   ffff000008c54000 0001000000000000
>  [88286.710757] 38e0: ffff8009768b3aa0 ffff0000080d8c7c ffff8009768b3b50 ffff80097ff8a5b0
>  [88286.718511] 3900: 0000800977325000 0000000000000000 0000000000000040 ffff80097ffc6180
>  [88286.726264] 3920: ffff8009768b3940 ffff0000088a8694 ffff80097ffc5800 0000000000000000
>  [88286.734017] 3940: ffff8009768b3960 ffff0000081919c0 ffff80097ffc5280 0000000000000001
>  [88286.741771] 3960: ffff8009768b3a50 ffff00000819206c ffff8009751b0e08 0000000000000000
>  [88286.749523] 3980: 0000000000000000 0000000000000000 0000000000000080 0000000000000000
>  [88286.757277] 39a0: ffff0000080d8ae4 0000000000000000 0000000000000000 ffff800977400028
>  [88286.765029] 39c0: 0000000000000000 0000000000000068 0000000000000040 0000000000000004
>  [88286.772783] 39e0: 0000000000000000 0000ffffb345b590 ffff000008088270 0000ffffb33d9a38
>  [88286.780537] [<ffff0000080d8c7c>] __queue_work+0x29c/0x3b8
>  [88286.785883] [<ffff0000080d8df8>] queue_work_on+0x60/0x78
>  [88286.791146] [<ffff000008764c68>] etm_setup_aux+0x178/0x238
>  [88286.796578] [<ffff000008183600>] rb_alloc_aux+0x228/0x310
>  [88286.801925] [<ffff00000817e564>] perf_mmap+0x404/0x5a8
>  [88286.807015] [<ffff0000081c60cc>] mmap_region+0x394/0x5c0
>  [88286.812276] [<ffff0000081c654c>] do_mmap+0x254/0x388
>  [88286.817191] [<ffff0000081a989c>] vm_mmap_pgoff+0xbc/0xe0
>  [88286.822452] [<ffff0000081c3ffc>] SyS_mmap_pgoff+0xac/0x228
>  [88286.827884] [<ffff000008088288>] sys_mmap+0x18/0x28
>  [88286.832714] [<ffff000008082f30>] el0_svc_naked+0x24/0x28
>
> The patch makes sure that the event_data->work is initialised
> properly before we could possibly use it.
>
> Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
>  drivers/hwtracing/coresight/coresight-etm-perf.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> index 26cfac3..df63315 100644
> --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> @@ -201,6 +201,7 @@ static void *etm_setup_aux(int event_cpu, void **pages,
>         event_data = alloc_event_data(event_cpu);
>         if (!event_data)
>                 return NULL;
> +       INIT_WORK(&event_data->work, free_event_data);
>
>         /*
>          * In theory nothing prevent tracers in a trace session from being
> @@ -217,8 +218,6 @@ static void *etm_setup_aux(int event_cpu, void **pages,
>         if (!sink)
>                 goto err;
>
> -       INIT_WORK(&event_data->work, free_event_data);
> -
>         mask = &event_data->mask;
>
>         /* Setup the path for each CPU in a trace session */
> --
> 2.7.4
>
>
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-- 
Mike Leach
Principal Engineer, ARM Ltd.
Blackburn Design Centre. UK