Messages in this thread Patch in this message |  | | Date | Wed, 14 Dec 2022 14:53:27 -0800 | From | Kees Cook <> | Subject | Re: [RFC PATCH] pstore: Switch pmsg_lock to an rt_mutex to avoid priority inversion |
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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
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