From: David Laight <David.Laight@ACULAB.COM>
To: 'Waiman Long' <longman@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Jann Horn <jannh@google.com>,
Vasiliy Kulikov <segoon@openwall.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Bernd Edlinger <bernd.edlinger@hotmail.de>,
Oleg Nesterov <oleg@redhat.com>,
"Christopher Yeoh" <cyeoh@au1.ibm.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
"Sargun Dhillon" <sargun@sargun.me>,
Christian Brauner <christian.brauner@ubuntu.com>,
Arnd Bergmann <arnd@arndb.de>,
Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: RE: [PATCH 2/3] rwsem: Implement down_read_interruptible
Date: Mon, 7 Dec 2020 16:58:34 +0000 [thread overview]
Message-ID: <c781c59872e742c2b64f1aa70c30d7e2@AcuMS.aculab.com> (raw)
In-Reply-To: <7be81903-14e3-7485-83e7-02e65e80e8c3@redhat.com>
From: Waiman Long
> Sent: 07 December 2020 15:34
>
> On 12/7/20 4:02 AM, Peter Zijlstra wrote:
> > On Thu, Dec 03, 2020 at 08:59:13PM -0500, Waiman Long wrote:
> >> On 12/3/20 3:11 PM, Eric W. Biederman wrote:
> >>> +static inline int __down_read_interruptible(struct rw_semaphore *sem)
> >>> +{
> >>> + if (!rwsem_read_trylock(sem)) {
> >>> + if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_INTERRUPTIBLE)))
> >>> + return -EINTR;
> >>> + DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
> >>> + } else {
> >>> + rwsem_set_reader_owned(sem);
> >>> + }
> >>> + return 0;
> >>> +}
> >>> +
> >>> static inline int __down_read_killable(struct rw_semaphore *sem)
> >>> {
> >>> if (!rwsem_read_trylock(sem)) {
> >>> @@ -1495,6 +1507,20 @@ void __sched down_read(struct rw_semaphore *sem)
> >>> }
> >>> EXPORT_SYMBOL(down_read);
> >>> +int __sched down_read_interruptible(struct rw_semaphore *sem)
> >>> +{
> >>> + might_sleep();
> >>> + rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
> >>> +
> >>> + if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_interruptible)) {
> >>> + rwsem_release(&sem->dep_map, _RET_IP_);
> >>> + return -EINTR;
> >>> + }
> >>> +
> >>> + return 0;
> >>> +}
> >>> +EXPORT_SYMBOL(down_read_interruptible);
> >>> +
> >>> int __sched down_read_killable(struct rw_semaphore *sem)
> >>> {
> >>> might_sleep();
> >> Acked-by: Waiman Long <longman@redhat.com>
> > Yeah, that seems correct.. There's an unfortunate amount of copy-paste
> > there though.
> >
> > Do we want to follow that up with something like this?
>
> I am actually thinking about similar streamlining once the patch lands.
>
> Your suggested changes look fine to me.
How much more difficult would it be to also add a timeout option?
I looked at adding one to the mutex code - and fell into a big pile
of replicated code.
ISTM that one the initial locked exchange (and spin) fails a few
extra instructions when heading for the sleep don't really matter
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-12-07 17:00 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 20:09 [PATCH 0/3] exec: Transform exec_update_mutex into a rw_semaphore Eric W. Biederman
2020-12-03 20:10 ` [PATCH 1/3] rwsem: Implement down_read_killable_nested Eric W. Biederman
2020-12-04 1:58 ` Waiman Long
2020-12-09 18:38 ` [tip: locking/core] " tip-bot2 for Eric W. Biederman
2020-12-03 20:11 ` [PATCH 2/3] rwsem: Implement down_read_interruptible Eric W. Biederman
2020-12-04 1:59 ` Waiman Long
2020-12-07 9:02 ` Peter Zijlstra
2020-12-07 15:33 ` Waiman Long
2020-12-07 16:58 ` David Laight [this message]
2020-12-07 19:02 ` Waiman Long
2020-12-08 9:12 ` David Laight
2020-12-08 12:32 ` Peter Zijlstra
2020-12-08 13:13 ` David Laight
2020-12-08 15:34 ` Waiman Long
2020-12-08 16:23 ` David Laight
2020-12-07 15:56 ` Eric W. Biederman
2020-12-08 14:52 ` Peter Zijlstra
2020-12-08 18:27 ` Eric W. Biederman
2020-12-09 18:36 ` Peter Zijlstra
2020-12-10 19:33 ` Eric W. Biederman
2020-12-11 8:16 ` Peter Zijlstra
2020-12-09 18:38 ` [tip: locking/core] locking/rwsem: Introduce rwsem_write_trylock() tip-bot2 for Peter Zijlstra
2020-12-09 18:38 ` [tip: locking/core] locking/rwsem: Fold __down_{read,write}*() tip-bot2 for Peter Zijlstra
2020-12-09 18:38 ` [tip: locking/core] locking/rwsem: Better collate rwsem_read_trylock() tip-bot2 for Peter Zijlstra
2020-12-09 18:38 ` [tip: locking/core] rwsem: Implement down_read_interruptible tip-bot2 for Eric W. Biederman
2020-12-03 20:12 ` [PATCH 3/3] exec: Transform exec_update_mutex into a rw_semaphore Eric W. Biederman
2020-12-04 16:08 ` Bernd Edlinger
2020-12-04 17:21 ` Linus Torvalds
2020-12-04 19:34 ` Eric W. Biederman
2020-12-04 20:10 ` Linus Torvalds
2020-12-04 20:30 ` Bernd Edlinger
2020-12-04 20:48 ` Linus Torvalds
2020-12-04 21:48 ` Davidlohr Bueso
2020-12-05 18:05 ` Eric W. Biederman
2020-12-07 9:15 ` Peter Zijlstra
2020-12-07 9:09 ` Peter Zijlstra
2020-12-07 18:40 ` Linus Torvalds
2020-12-08 8:34 ` [PATCH] perf: Break deadlock involving exec_update_mutex Peter Zijlstra
2020-12-08 18:37 ` Linus Torvalds
2020-12-10 18:38 ` Davidlohr Bueso
2020-12-10 19:40 ` Eric W. Biederman
2020-12-05 17:43 ` [PATCH 3/3] exec: Transform exec_update_mutex into a rw_semaphore Eric W. Biederman
2020-12-04 17:39 ` Eric W. Biederman
2020-12-03 22:42 ` [PATCH 0/3] " Linus Torvalds
2020-12-04 1:56 ` Waiman Long
2020-12-04 4:54 ` Davidlohr Bueso
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