From: Peter Zijlstra <peterz@infradead.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
Ingo Molnar <mingo@redhat.com>, Waiman Long <longman@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>, Will Deacon <will@kernel.org>,
Roman Penyaev <rpenyaev@suse.de>,
Shakeel Butt <shakeelb@google.com>
Subject: Re: [PATCH] locking/rwlocks: do not starve writers
Date: Fri, 17 Jun 2022 14:07:27 +0200 [thread overview]
Message-ID: <YqxufxqsnHjVfQOs@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20220617091039.2257083-1-eric.dumazet@gmail.com>
On Fri, Jun 17, 2022 at 02:10:39AM -0700, Eric Dumazet wrote:
> --- a/kernel/locking/qrwlock.c
> +++ b/kernel/locking/qrwlock.c
> @@ -23,16 +23,6 @@ void queued_read_lock_slowpath(struct qrwlock *lock)
> /*
> * Readers come here when they cannot get the lock without waiting
> */
> - if (unlikely(in_interrupt())) {
> - /*
> - * Readers in interrupt context will get the lock immediately
> - * if the writer is just waiting (not holding the lock yet),
> - * so spin with ACQUIRE semantics until the lock is available
> - * without waiting in the queue.
> - */
> - atomic_cond_read_acquire(&lock->cnts, !(VAL & _QW_LOCKED));
> - return;
> - }
> atomic_sub(_QR_BIAS, &lock->cnts);
>
> trace_contention_begin(lock, LCB_F_SPIN | LCB_F_READ);
This is known to break tasklist_lock.
next prev parent reply other threads:[~2022-06-17 12:07 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-17 9:10 [PATCH] locking/rwlocks: do not starve writers Eric Dumazet
2022-06-17 12:07 ` Peter Zijlstra [this message]
2022-06-17 14:43 ` Waiman Long
2022-06-17 14:57 ` Shakeel Butt
2022-06-17 15:00 ` Waiman Long
2022-06-17 15:24 ` Eric Dumazet
2022-06-17 15:56 ` Peter Zijlstra
2022-06-17 17:41 ` Waiman Long
2022-06-17 17:45 ` Eric Dumazet
2022-06-17 18:57 ` Waiman Long
2022-06-17 19:04 ` Peter Zijlstra
2022-06-17 19:10 ` Eric Dumazet
2022-06-17 19:19 ` Linus Torvalds
2022-06-17 19:25 ` Eric Dumazet
2022-06-17 19:34 ` Linus Torvalds
2022-06-17 19:39 ` Eric Dumazet
2022-06-17 19:48 ` Linus Torvalds
2022-06-20 7:25 ` Peter Zijlstra
2022-06-21 16:55 ` Eric W. Biederman
2022-06-17 21:58 ` David Laight
2022-06-17 19:34 ` Shakeel Butt
2022-06-17 19:08 ` Linus Torvalds
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