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Re: Draft pthread_spin_init(2) manual page
- From: Zack Weinberg <zackw at panix dot com>
- To: "Michael Kerrisk (man-pages)" <mtk dot manpages at gmail dot com>
- Cc: linux-man <linux-man at vger dot kernel dot org>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>, Thomas Gleixner <tglx at linutronix dot de>, Peter Zijlstra <peterz at infradead dot org>, Ingo Molnar <mingo at redhat dot com>
- Date: Wed, 18 Oct 2017 13:44:22 -0400
- Subject: Re: Draft pthread_spin_init(2) manual page
- Authentication-results: sourceware.org; auth=none
- References: <CAKgNAkh+wT26bTkWzyWg7K6S8CAcbbGoDx5Tha4QzP5sYKC7RA@mail.gmail.com>
On Wed, Oct 18, 2017 at 4:10 AM, Michael Kerrisk (man-pages)
<mtk.manpages@gmail.com> wrote:
> Hello all,
>
> I recently drafted a manual page for the pthread_spin_init() and
> pthread_spin_destroy() APIs. Comments and suggestions for improvements
> would be most welcome.
This should probably cross-reference the pthread_mutex_* manpages and
say when it is appropriate to use which. I see you already have some
of that...
> NOTES
> Spin locks should be employed in conjunction with real-time sched‐
> uling policies (SCHED_FIFO, or possibly SCHED_RR). Use of spin
> locks with nondeterministic scheduling policies such as
> SCHED_OTHER probably indicates a design mistake. The problem is
> that if a thread operating under such a policy is scheduled off
> the CPU while it holds a spin lock, then other threads will waste
> time spinning on the lock until the lock holder is once more
> rescheduled and releases the lock.
>
> Warning: if threads create a deadlock situation while employing
> spin locks, those threads will spin forever consuming CPU time.
but you might want to begin with something like "Most programs should
use mutexes (pthread_mutex_init(3)) instead of spin locks. Spin locks
are primarily useful in conjunction with real-time scheduling ..."
Also, this is important enough that I'd put it in the DESCRIPTION.
zw