lkml.org 
[lkml]   [2022]   [Dec]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [RFC PATCH] pstore: Switch pmsg_lock to an rt_mutex to avoid priority inversion
On Mon, Dec 05, 2022 at 08:32:53PM +0000, John Stultz wrote:
> Wei Wang reported seeing priority inversion caused latencies
> caused by contention on pmsg_lock, and suggested it be switched
> to a rt_mutex.
>
> I was initially hesitant this would help, as the tasks in that
> trace all seemed to be SCHED_NORMAL, so the benefit would be
> limited to only nice boosting.
>
> However, another similar issue was raised where the priority
> inversion was seen did involve a blocked RT task so it is clear
> this would be helpful in that case.
>
> Feedback would be appreciate!

This looks fine to me. Is there an appropriate "Fixes:" tag that could
be used?

-Kees

>
> Cc: Wei Wang <wvw@google.com>
> Cc: Midas Chien<midaschieh@google.com>
> Cc: Connor O'Brien <connoro@google.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Anton Vorontsov <anton@enomsg.org>
> Cc: Colin Cross <ccross@android.com>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: kernel-team@android.com
> Reported-by: Wei Wang <wvw@google.com>
> Signed-off-by: John Stultz <jstultz@google.com>
> ---
> fs/pstore/pmsg.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/pstore/pmsg.c b/fs/pstore/pmsg.c
> index d8542ec2f38c..18cf94b597e0 100644
> --- a/fs/pstore/pmsg.c
> +++ b/fs/pstore/pmsg.c
> @@ -7,9 +7,10 @@
> #include <linux/device.h>
> #include <linux/fs.h>
> #include <linux/uaccess.h>
> +#include <linux/rtmutex.h>
> #include "internal.h"
>
> -static DEFINE_MUTEX(pmsg_lock);
> +static DEFINE_RT_MUTEX(pmsg_lock);
>
> static ssize_t write_pmsg(struct file *file, const char __user *buf,
> size_t count, loff_t *ppos)
> @@ -28,9 +29,9 @@ static ssize_t write_pmsg(struct file *file, const char __user *buf,
> if (!access_ok(buf, count))
> return -EFAULT;
>
> - mutex_lock(&pmsg_lock);
> + rt_mutex_lock(&pmsg_lock);
> ret = psinfo->write_user(&record, buf);
> - mutex_unlock(&pmsg_lock);
> + rt_mutex_unlock(&pmsg_lock);
> return ret ? ret : count;
> }
>
> --
> 2.39.0.rc0.267.gcb52ba06e7-goog
>

--
Kees Cook

\
 
 \ /
  Last update: 2022-12-14 23:54    [W:0.626 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site