linux-kernel - Re: [PATCH v4] ACPI: battery: prevent sysfs_add

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Message-ID: <2025091322-resilient-bottle-6d85@gregkh>
Date: Sat, 13 Sep 2025 09:33:36 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: GuangFei Luo <luogf2025@....com>
Cc: rafael@...nel.org, dan.carpenter@...aro.org, lenb@...nel.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, lkp@...el.com, sre@...nel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v4] ACPI: battery: prevent sysfs_add_battery re-entry on
 rapid events

On Sat, Sep 13, 2025 at 03:19:25PM +0800, GuangFei Luo wrote:
> v4:
>   - Uses guard(mutex) for battery->sysfs_lock in sysfs_add_battery().
>   - Since sysfs_add_battery() now handles the battery->bat check with
>     proper locking,the extra if (!battery->bat) check at the call site
>     has become redundant.
> 
> v3:
>   - Modified the earlier approach: since sysfs_add_battery() is invoked
>     from multiple places, the most reliable way is to add the lock inside
>     the function itself.
>   - sysfs_remove_battery() had a similar race issue in the past, which was
>     fixed by adding a lock as well. Reference:
>     https://lore.kernel.org/all/9c921c22a7f33397a6774d7fa076db9b6a0fd669
> 	.1312318300.git.len.brown@...el.com/
> 
> v2:
>  - Fix missing mutex_unlock in acpi_battery_update()
>    (Reported-by: kernel test robot)
> 
> v1:
> When removing and reinserting the laptop battery, ACPI can trigger
> two notifications in quick succession:

Again, all of this goes below the --- line, not above it.