From: Frederic Weisbecker <fweisbec@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] nohz: Change tick_dep_mask from 'unsigned long' to 'unsigned int'
Date: Tue, 15 Mar 2016 18:28:04 +0100 [thread overview]
Message-ID: <20160315172803.GB5058@lerouge> (raw)
In-Reply-To: <CA+55aFzW1eSZGSC7gQdTOHqPHq5UEVR+_OvdxbAhGiCFSPcf7g@mail.gmail.com>
On Tue, Mar 15, 2016 at 09:30:49AM -0700, Linus Torvalds wrote:
> On Tue, Mar 15, 2016 at 5:15 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > Hm, so the problem I did not consider is the following:
> >
> > triton:~/tip> git grep tick_dep_mask kernel | grep _bit
> > kernel/time/tick-sched.c: clear_bit(bit, &ts->tick_dep_mask);
> > kernel/time/tick-sched.c: clear_bit(bit, &tsk->tick_dep_mask);
> > kernel/time/tick-sched.c: clear_bit(bit, &sig->tick_dep_mask);
Ah! Now I remember why I used unsigned long :-s
>
> Ahh. I missed that too.
>
> Ok, leave the 64-bit field for now, while we think about this. But one
> option is to just use "atomic_andnot()" instead of clear_bit().
>
> That would imply using an "atomic_t", which would be fairly natural
> (and would be 32-bit).
I can try that. And then we would end up with atomic_fetch_or() and maybe
the scheduler could keep its ad-hoc version until thread_info types get unified
(if that's possible).
>
> And wouldn't it be so nice if "thread_info->flags" would just be
> atomic_t too. Right now we use a mixture of bit-ops and ACCESS_ONCE()
> (and many codepaths then doing neither, and just accessing it
> directly, ignoring any races.
>
> Oh well.
I can try that too while at it :-)
next prev parent reply other threads:[~2016-03-15 17:28 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-14 12:32 [GIT PULL] NOHZ updates for v4.6 Ingo Molnar
2016-03-15 2:44 ` Linus Torvalds
2016-03-15 8:42 ` Peter Zijlstra
2016-03-15 9:49 ` Ingo Molnar
2016-03-15 9:32 ` [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()' Ingo Molnar
2016-03-15 10:50 ` Peter Zijlstra
2016-03-15 12:08 ` Ingo Molnar
2016-03-15 12:42 ` Peter Zijlstra
2016-03-15 11:06 ` Peter Zijlstra
2016-03-15 11:59 ` Peter Zijlstra
2016-03-15 12:01 ` Ingo Molnar
2016-03-15 12:32 ` Ingo Molnar
2016-03-15 12:37 ` Ingo Molnar
2016-03-15 13:17 ` Peter Zijlstra
2016-03-15 12:21 ` [PATCH v2] " Ingo Molnar
2016-03-15 13:26 ` Peter Zijlstra
2016-03-16 8:04 ` Ingo Molnar
2016-03-16 8:29 ` Peter Zijlstra
2016-03-15 17:08 ` Frederic Weisbecker
2016-03-16 8:14 ` Ingo Molnar
2016-03-17 0:54 ` Frederic Weisbecker
2016-03-15 16:18 ` [PATCH] " Linus Torvalds
2016-03-15 9:53 ` [PATCH] nohz: Change tick_dep_mask from 'unsigned long' to 'unsigned int' Ingo Molnar
2016-03-15 12:15 ` Ingo Molnar
2016-03-15 16:30 ` Linus Torvalds
2016-03-15 17:28 ` Frederic Weisbecker [this message]
2016-03-15 17:36 ` Linus Torvalds
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