Date: Mon, 22 Feb 2010 23:34:11 -0800 (PST) From: Shrivatsan <shrivatsan_v@yahoo.com> To: freebsd-hackers@FreeBSD.org Cc: shrivatsan@gmail.com Subject: sched_lock mutex and sleepq_wait Message-ID: <986041.3700.qm@web112005.mail.gq1.yahoo.com>
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Hi,
I am trying to understand how msleep() routine suspends the currently
executing thread. I see that msleep() calls sleepq_wait().
What I don't understand here is the way in which sched_lock mutex is
handled.
I took the following snippet from FreeBSD 6:
sleepq_wait(void *wchan)
{
MPASS(!(curthread->td_flags & TDF_SINTR));
mtx_lock_spin(&sched_lock);
sleepq_switch(wchan);
mtx_unlock_spin(&sched_lock);
}
sched_lock mutex is held, and sleepq_switch() eventually calls
cpu_switch() which switches to a new thread.
I don't exactly understand when the sched_lock mutex is released.
Can someone please help me?
Thanks,
-shrivatsan
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