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authorJohn Stultz <jstultz@google.com>2022-12-15 02:18:34 +0300
committerKees Cook <keescook@chromium.org>2022-12-15 06:37:42 +0300
commit76d62f24db07f22ccf9bc18ca793c27d4ebef721 (patch)
treea1a53f0abbae596ad1bb60836c3447092b16c5b7 /fs/pstore
parente6b842741b4f39007215fd7e545cb55aa3d358a2 (diff)
downloadlinux-76d62f24db07f22ccf9bc18ca793c27d4ebef721.tar.xz
pstore: Switch pmsg_lock to an rt_mutex to avoid priority inversion
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. 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 Fixes: 9d5438f462ab ("pstore: Add pmsg - user-space accessible pstore object") Reported-by: Wei Wang <wvw@google.com> Signed-off-by: John Stultz <jstultz@google.com> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20221214231834.3711880-1-jstultz@google.com
Diffstat (limited to 'fs/pstore')
-rw-r--r--fs/pstore/pmsg.c7
1 files 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;
}