| Message ID | 20210406221952.50399-1-ahalaney@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [RT] locking/rwsem-rt: Remove might_sleep() in __up_read() | expand |
On Tue, Apr 06, 2021 at 05:19:52PM -0500, Andrew Halaney wrote: > There's no chance of sleeping here, the reader is giving up the > lock and possibly waking up the writer who is waiting on it. > > Reported-by: Chunyu Hu <chuhu@redhat.com> > Signed-off-by: Andrew Halaney <ahalaney@redhat.com> > --- > Hello, > > I ran into a warning caused by this, and I think the warning is > incorrect. Please let me know if I'm wrong! > I'm working off of linux-5.12.y-rt, but this applies cleanly to older > stable branches as well. > > Thanks, > Andrew > > kernel/locking/rwsem-rt.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/kernel/locking/rwsem-rt.c b/kernel/locking/rwsem-rt.c > index 274172d5bb3a..b61edc4dcb73 100644 > --- a/kernel/locking/rwsem-rt.c > +++ b/kernel/locking/rwsem-rt.c > @@ -198,7 +198,6 @@ void __up_read(struct rw_semaphore *sem) > if (!atomic_dec_and_test(&sem->readers)) > return; > > - might_sleep(); > raw_spin_lock_irq(&m->wait_lock); > /* > * Wake the writer, i.e. the rtmutex owner. It might release the > -- > 2.30.2 > Just a gentle follow up, any feedback? Thanks, Andrew
On Mon, Apr 26 2021 at 11:42, Andrew Halaney wrote: > On Tue, Apr 06, 2021 at 05:19:52PM -0500, Andrew Halaney wrote: >> There's no chance of sleeping here, the reader is giving up the >> lock and possibly waking up the writer who is waiting on it. >> >> Reported-by: Chunyu Hu <chuhu@redhat.com> >> Signed-off-by: Andrew Halaney <ahalaney@redhat.com> >> --- >> Hello, >> >> I ran into a warning caused by this, and I think the warning is >> incorrect. Please let me know if I'm wrong! >> I'm working off of linux-5.12.y-rt, but this applies cleanly to older >> stable branches as well. >> >> Thanks, >> Andrew >> >> kernel/locking/rwsem-rt.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/kernel/locking/rwsem-rt.c b/kernel/locking/rwsem-rt.c >> index 274172d5bb3a..b61edc4dcb73 100644 >> --- a/kernel/locking/rwsem-rt.c >> +++ b/kernel/locking/rwsem-rt.c >> @@ -198,7 +198,6 @@ void __up_read(struct rw_semaphore *sem) >> if (!atomic_dec_and_test(&sem->readers)) >> return; >> >> - might_sleep(); >> raw_spin_lock_irq(&m->wait_lock); >> /* >> * Wake the writer, i.e. the rtmutex owner. It might release the >> -- >> 2.30.2 > > Just a gentle follow up, any feedback? Looks correct. Will go into the next rt-release. Thanks, tglx
On Mon, Apr 26, 2021 at 08:16:34PM +0200, Thomas Gleixner wrote: > On Mon, Apr 26 2021 at 11:42, Andrew Halaney wrote: > > On Tue, Apr 06, 2021 at 05:19:52PM -0500, Andrew Halaney wrote: > >> There's no chance of sleeping here, the reader is giving up the > >> lock and possibly waking up the writer who is waiting on it. > >> > >> Reported-by: Chunyu Hu <chuhu@redhat.com> > >> Signed-off-by: Andrew Halaney <ahalaney@redhat.com> > >> --- > >> Hello, > >> > >> I ran into a warning caused by this, and I think the warning is > >> incorrect. Please let me know if I'm wrong! > >> I'm working off of linux-5.12.y-rt, but this applies cleanly to older > >> stable branches as well. > >> > >> Thanks, > >> Andrew > >> > >> kernel/locking/rwsem-rt.c | 1 - > >> 1 file changed, 1 deletion(-) > >> > >> diff --git a/kernel/locking/rwsem-rt.c b/kernel/locking/rwsem-rt.c > >> index 274172d5bb3a..b61edc4dcb73 100644 > >> --- a/kernel/locking/rwsem-rt.c > >> +++ b/kernel/locking/rwsem-rt.c > >> @@ -198,7 +198,6 @@ void __up_read(struct rw_semaphore *sem) > >> if (!atomic_dec_and_test(&sem->readers)) > >> return; > >> > >> - might_sleep(); > >> raw_spin_lock_irq(&m->wait_lock); > >> /* > >> * Wake the writer, i.e. the rtmutex owner. It might release the > >> -- > >> 2.30.2 > > > > Just a gentle follow up, any feedback? > > Looks correct. Will go into the next rt-release. > > Thanks, > > tglx > Hi Thomas, I see a new release (v5.13-rt1) was created, and with it rwsem was overhauled entirely making this patch pointless for linux-rt-devel. That being said, it's a little unclear to me how RT only patches make their way to the maintained branches over in linux-stable-rt. I think it should be applied to: v4.9-rt v4.14-rt v4.19-rt v5.4-rt v5.10-rt to remove the incorrect warning, unless those branches plan to backport the latest RT patchset with the new rwsem implementation. Is there a proper way for me signal that? Thanks, Andrew
Andrew, On Thu, Jul 08 2021 at 14:51, Andrew Halaney wrote: Cc+ stable-rt folks and leave context untrimmed. > On Mon, Apr 26, 2021 at 08:16:34PM +0200, Thomas Gleixner wrote: >> On Mon, Apr 26 2021 at 11:42, Andrew Halaney wrote: >> > On Tue, Apr 06, 2021 at 05:19:52PM -0500, Andrew Halaney wrote: >> >> There's no chance of sleeping here, the reader is giving up the >> >> lock and possibly waking up the writer who is waiting on it. >> >> >> >> Reported-by: Chunyu Hu <chuhu@redhat.com> >> >> Signed-off-by: Andrew Halaney <ahalaney@redhat.com> >> >> --- >> >> Hello, >> >> >> >> I ran into a warning caused by this, and I think the warning is >> >> incorrect. Please let me know if I'm wrong! >> >> I'm working off of linux-5.12.y-rt, but this applies cleanly to older >> >> stable branches as well. >> >> >> >> Thanks, >> >> Andrew >> >> >> >> kernel/locking/rwsem-rt.c | 1 - >> >> 1 file changed, 1 deletion(-) >> >> >> >> diff --git a/kernel/locking/rwsem-rt.c b/kernel/locking/rwsem-rt.c >> >> index 274172d5bb3a..b61edc4dcb73 100644 >> >> --- a/kernel/locking/rwsem-rt.c >> >> +++ b/kernel/locking/rwsem-rt.c >> >> @@ -198,7 +198,6 @@ void __up_read(struct rw_semaphore *sem) >> >> if (!atomic_dec_and_test(&sem->readers)) >> >> return; >> >> >> >> - might_sleep(); >> >> raw_spin_lock_irq(&m->wait_lock); >> >> /* >> >> * Wake the writer, i.e. the rtmutex owner. It might release the >> >> -- >> >> 2.30.2 >> > >> > Just a gentle follow up, any feedback? >> >> Looks correct. Will go into the next rt-release. >> >> Thanks, >> >> tglx >> > > Hi Thomas, > > I see a new release (v5.13-rt1) was created, and with it rwsem > was overhauled entirely making this patch pointless for linux-rt-devel. > > That being said, it's a little unclear to me how RT only patches > make their way to the maintained branches over in linux-stable-rt. > I think it should be applied to: > v4.9-rt > v4.14-rt > v4.19-rt > v5.4-rt > v5.10-rt > to remove the incorrect warning, unless those branches plan to backport > the latest RT patchset with the new rwsem implementation. Is there a > proper way for me signal that? See Cc. Thanks, tglx
diff --git a/kernel/locking/rwsem-rt.c b/kernel/locking/rwsem-rt.c index 274172d5bb3a..b61edc4dcb73 100644 --- a/kernel/locking/rwsem-rt.c +++ b/kernel/locking/rwsem-rt.c @@ -198,7 +198,6 @@ void __up_read(struct rw_semaphore *sem) if (!atomic_dec_and_test(&sem->readers)) return; - might_sleep(); raw_spin_lock_irq(&m->wait_lock); /* * Wake the writer, i.e. the rtmutex owner. It might release the
There's no chance of sleeping here, the reader is giving up the lock and possibly waking up the writer who is waiting on it. Reported-by: Chunyu Hu <chuhu@redhat.com> Signed-off-by: Andrew Halaney <ahalaney@redhat.com> --- Hello, I ran into a warning caused by this, and I think the warning is incorrect. Please let me know if I'm wrong! I'm working off of linux-5.12.y-rt, but this applies cleanly to older stable branches as well. Thanks, Andrew kernel/locking/rwsem-rt.c | 1 - 1 file changed, 1 deletion(-)