Re: [PATCH] PM / devfreq: Add missing locking while setting suspend_freq

[Chanwoo Choi <cw00.choi@samsung.com>]

Dear Rafael,

Could you take this patch directly into linux-pm.git for v5.5-rc1?

Because the devfreq pull-request for v5.5-rc1 contained issue. This patch
fix the issue of following patch[1].
[1] https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/commit/?h=linux-next&id=2abb0d5268ae7b5ddf82099b1f8d5aa8414637d4


---
Hi Marek,

Thanks for the fixup.
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>

Regards,
Chanwoo Choi


On 11/12/19 7:47 PM, Marek Szyprowski wrote:
> Commit 2abb0d5268ae ("PM / devfreq: Lock devfreq in trans_stat_show")
> revealed a missing locking while calling devfreq_update_status() function
> during suspend/resume cycle.
> 
> Code analysis revealed that devfreq_set_target() function was called
> without needed locks held for setting device specific suspend_freq if such
> has been defined. This patch fixes that by adding the needed locking, what
> fixes following kernel warning on Exynos4412-based OdroidU3 board during
> system suspend:
> 
> PM: suspend entry (deep)
> Filesystems sync: 0.002 seconds
> Freezing user space processes ... (elapsed 0.001 seconds) done.
> OOM killer disabled.
> Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
> ------------[ cut here ]------------
> WARNING: CPU: 2 PID: 1385 at drivers/devfreq/devfreq.c:204 devfreq_update_status+0xc0/0x188
> Modules linked in:
> CPU: 2 PID: 1385 Comm: rtcwake Not tainted 5.4.0-rc6-next-20191111 #6848
> Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> [<c0112588>] (unwind_backtrace) from [<c010e070>] (show_stack+0x10/0x14)
> [<c010e070>] (show_stack) from [<c0afb010>] (dump_stack+0xb4/0xe0)
> [<c0afb010>] (dump_stack) from [<c01272e0>] (__warn+0xf4/0x10c)
> [<c01272e0>] (__warn) from [<c01273a8>] (warn_slowpath_fmt+0xb0/0xb8)
> [<c01273a8>] (warn_slowpath_fmt) from [<c07d105c>] (devfreq_update_status+0xc0/0x188)
> [<c07d105c>] (devfreq_update_status) from [<c07d2d70>] (devfreq_set_target+0xb0/0x15c)
> [<c07d2d70>] (devfreq_set_target) from [<c07d3598>] (devfreq_suspend+0x2c/0x64)
> [<c07d3598>] (devfreq_suspend) from [<c05de0b0>] (dpm_suspend+0xa4/0x57c)
> [<c05de0b0>] (dpm_suspend) from [<c05def74>] (dpm_suspend_start+0x98/0xa0)
> [<c05def74>] (dpm_suspend_start) from [<c0195b58>] (suspend_devices_and_enter+0xec/0xc74)
> [<c0195b58>] (suspend_devices_and_enter) from [<c0196a20>] (pm_suspend+0x340/0x410)
> [<c0196a20>] (pm_suspend) from [<c019480c>] (state_store+0x6c/0xc8)
> [<c019480c>] (state_store) from [<c033fc50>] (kernfs_fop_write+0x10c/0x228)
> [<c033fc50>] (kernfs_fop_write) from [<c02a6d3c>] (__vfs_write+0x30/0x1d0)
> [<c02a6d3c>] (__vfs_write) from [<c02a9afc>] (vfs_write+0xa4/0x180)
> [<c02a9afc>] (vfs_write) from [<c02a9d58>] (ksys_write+0x60/0xd8)
> [<c02a9d58>] (ksys_write) from [<c0101000>] (ret_fast_syscall+0x0/0x28)
> Exception stack(0xed3d7fa8 to 0xed3d7ff0)
> ...
> irq event stamp: 9667
> hardirqs last  enabled at (9679): [<c0b1e7c4>] _raw_spin_unlock_irq+0x20/0x58
> hardirqs last disabled at (9698): [<c0b16a20>] __schedule+0xd8/0x818
> softirqs last  enabled at (9694): [<c01026fc>] __do_softirq+0x4fc/0x5fc
> softirqs last disabled at (9719): [<c012fe68>] irq_exit+0x16c/0x170
> ---[ end trace 41ac5b57d046bdbc ]---
> ------------[ cut here ]------------
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/devfreq/devfreq.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 94fb8e821e12..65a4b6cf3fa5 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -957,7 +957,9 @@ int devfreq_suspend_device(struct devfreq *devfreq)
>  	}
>  
>  	if (devfreq->suspend_freq) {
> +		mutex_lock(&devfreq->lock);
>  		ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
> +		mutex_unlock(&devfreq->lock);
>  		if (ret)
>  			return ret;
>  	}
> @@ -985,7 +987,9 @@ int devfreq_resume_device(struct devfreq *devfreq)
>  		return 0;
>  
>  	if (devfreq->resume_freq) {
> +		mutex_lock(&devfreq->lock);
>  		ret = devfreq_set_target(devfreq, devfreq->resume_freq, 0);
> +		mutex_unlock(&devfreq->lock);
>  		if (ret)
>  			return ret;
>  	}
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics