Re: [PATCH] coresight: cti: Fix hang in cti_disable_hw()

[James Clark]

On 05/10/2022 14:14, James Clark wrote:
> cti_enable_hw() and cti_disable_hw() are called from an atomic context
> so shouldn't use runtime PM because it can result in a sleep when
> communicating with firmware.

Hi Mike,

Are you able to test this on a Dragonboard please? I've only tested on
Juno so far.

Thanks
James

> 
> Since commit 3c6656337852 ("Revert "firmware: arm_scmi: Add clock
> management to the SCMI power domain""), this causes a hang on Juno when
> running the Perf Coresight tests or running this command:
> 
>   perf record -e cs_etm//u -- ls
> 
> This was also missed until the revert commit because pm_runtime_put()
> was called with the wrong device until commit 692c9a499b28 ("coresight:
> cti: Correct the parameter for pm_runtime_put")
> 
> With lock and scheduler debugging enabled the following is output:
> 
>    coresight cti_sys0: cti_enable_hw -- dev:cti_sys0  parent: 20020000.cti
>    BUG: sleeping function called from invalid context at drivers/base/power/runtime.c:1151
>    in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 330, name: perf-exec
>    preempt_count: 2, expected: 0
>    RCU nest depth: 0, expected: 0
>    INFO: lockdep is turned off.
>    irq event stamp: 0
>    hardirqs last  enabled at (0): [<0000000000000000>] 0x0
>    hardirqs last disabled at (0): [<ffff80000822b394>] copy_process+0xa0c/0x1948
>    softirqs last  enabled at (0): [<ffff80000822b394>] copy_process+0xa0c/0x1948
>    softirqs last disabled at (0): [<0000000000000000>] 0x0
>    CPU: 3 PID: 330 Comm: perf-exec Not tainted 6.0.0-00053-g042116d99298 #7
>    Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform, BIOS EDK II Sep 13 2022
>    Call trace:
>     dump_backtrace+0x134/0x140
>     show_stack+0x20/0x58
>     dump_stack_lvl+0x8c/0xb8
>     dump_stack+0x18/0x34
>     __might_resched+0x180/0x228
>     __might_sleep+0x50/0x88
>     __pm_runtime_resume+0xac/0xb0
>     cti_enable+0x44/0x120
>     coresight_control_assoc_ectdev+0xc0/0x150
>     coresight_enable_path+0xb4/0x288
>     etm_event_start+0x138/0x170
>     etm_event_add+0x48/0x70
>     event_sched_in.isra.122+0xb4/0x280
>     merge_sched_in+0x1fc/0x3d0
>     visit_groups_merge.constprop.137+0x16c/0x4b0
>     ctx_sched_in+0x114/0x1f0
>     perf_event_sched_in+0x60/0x90
>     ctx_resched+0x68/0xb0
>     perf_event_exec+0x138/0x508
>     begin_new_exec+0x52c/0xd40
>     load_elf_binary+0x6b8/0x17d0
>     bprm_execve+0x360/0x7f8
>     do_execveat_common.isra.47+0x218/0x238
>     __arm64_sys_execve+0x48/0x60
>     invoke_syscall+0x4c/0x110
>     el0_svc_common.constprop.4+0xfc/0x120
>     do_el0_svc+0x34/0xc0
>     el0_svc+0x40/0x98
>     el0t_64_sync_handler+0x98/0xc0
>     el0t_64_sync+0x170/0x174
> 
> Fix the issue by removing the runtime PM calls completely. They are not
> needed here because it must have already been done when building the
> path for a trace.
> 
> Fixes: 835d722ba10a ("coresight: cti: Initial CoreSight CTI Driver")
> Reported-by: Aishwarya TCV <Aishwarya.TCV@xxxxxxx>
> Reported-by: Cristian Marussi <Cristian.Marussi@xxxxxxx>
> Signed-off-by: Suzuki Poulose <Suzuki.Poulose@xxxxxxx>
> Signed-off-by: James Clark <james.clark@xxxxxxx>
> ---
>  drivers/hwtracing/coresight/coresight-cti-core.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c b/drivers/hwtracing/coresight/coresight-cti-core.c
> index 8988b2ed2ea6..c5f7fc4e2552 100644
> --- a/drivers/hwtracing/coresight/coresight-cti-core.c
> +++ b/drivers/hwtracing/coresight/coresight-cti-core.c
> @@ -94,7 +94,6 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)
>  	unsigned long flags;
>  	int rc = 0;
>  
> -	pm_runtime_get_sync(dev->parent);
>  	spin_lock_irqsave(&drvdata->spinlock, flags);
>  
>  	/* no need to do anything if enabled or unpowered*/
> @@ -119,7 +118,6 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)
>  	/* cannot enable due to error */
>  cti_err_not_enabled:
>  	spin_unlock_irqrestore(&drvdata->spinlock, flags);
> -	pm_runtime_put(dev->parent);
>  	return rc;
>  }
>  
> @@ -175,7 +173,6 @@ static int cti_disable_hw(struct cti_drvdata *drvdata)
>  	coresight_disclaim_device_unlocked(csdev);
>  	CS_LOCK(drvdata->base);
>  	spin_unlock(&drvdata->spinlock);
> -	pm_runtime_put(dev->parent);
>  	return 0;
>  
>  	/* not disabled this call */