From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>, boqun.feng@gmail.com
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org,
Ingo Molnar <mingo@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Mike Galbraith <efault@gmx.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>
Subject: Re: [PATCH 3/4] locking/rwbase: Fix rwbase_write_lock() vs __rwbase_read_lock()
Date: Tue, 14 Sep 2021 09:45:12 +0200 [thread overview]
Message-ID: <87k0jjeh2v.ffs@tglx> (raw)
In-Reply-To: <20210909110203.893845303@infradead.org>
On Thu, Sep 09 2021 at 12:59, Peter Zijlstra wrote:
> Boqun noticed that the write-trylock sequence of load+set is broken in
> rwbase_write_lock()'s wait-loop since they're not both under the same
> wait_lock instance.
Confused.
lock(); A
for (; atomic_read(readers);) {
...
unlock();
..
lock(); B
}
atomic_set();
unlock(); A or B
The read/set is always in the same lock instance.
> Restructure the code to make this more obvious and correct.
I agree that it's easier to read, but I disagree that it makes the code
more correct.
Thanks,
tglx
next prev parent reply other threads:[~2021-09-14 7:46 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-09 10:59 [PATCH 0/4] locking/rwbase: Assorted fixes Peter Zijlstra
2021-09-09 10:59 ` [PATCH 1/4] sched/wakeup: Strengthen current_save_and_set_rtlock_wait_state() Peter Zijlstra
2021-09-09 13:45 ` Will Deacon
2021-09-09 14:27 ` Peter Zijlstra
2021-09-10 12:57 ` Will Deacon
2021-09-10 13:17 ` Peter Zijlstra
2021-09-10 14:01 ` Peter Zijlstra
2021-09-10 15:06 ` Will Deacon
2021-09-10 16:07 ` Waiman Long
2021-09-10 17:09 ` Peter Zijlstra
2021-09-12 3:57 ` Boqun Feng
2021-09-10 12:45 ` Sebastian Andrzej Siewior
2021-09-13 22:08 ` Thomas Gleixner
2021-09-13 22:52 ` Thomas Gleixner
2021-09-14 6:45 ` Peter Zijlstra
2021-09-09 10:59 ` [PATCH 2/4] locking/rwbase: Properly match set_and_save_state() to restore_state() Peter Zijlstra
2021-09-09 13:53 ` Will Deacon
2021-09-14 7:31 ` Thomas Gleixner
2021-09-16 11:59 ` [tip: locking/urgent] " tip-bot2 for Peter Zijlstra
2021-09-09 10:59 ` [PATCH 3/4] locking/rwbase: Fix rwbase_write_lock() vs __rwbase_read_lock() Peter Zijlstra
2021-09-14 7:45 ` Thomas Gleixner [this message]
2021-09-14 13:59 ` Peter Zijlstra
2021-09-14 15:00 ` Thomas Gleixner
2021-09-16 11:59 ` [tip: locking/urgent] locking/rwbase: Extract __rwbase_write_trylock() tip-bot2 for Peter Zijlstra
2021-09-09 10:59 ` [PATCH 4/4] locking/rwbase: Take care of ordering guarantee for fastpath reader Peter Zijlstra
2021-09-14 7:46 ` Thomas Gleixner
2021-09-16 11:59 ` [tip: locking/urgent] " tip-bot2 for Boqun Feng
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