Date: Tue, 15 Jul 2008 16:56:10 +0300 From: "Yony Yossef" <yonyossef.lists@gmail.com> To: "Kris Kennaway" <kris@freebsd.org> Cc: freebsd-questions@freebsd.org Subject: Re: options WITNESS and locks Message-ID: <20def4870807150656y761a8bcfo858b85b760d0f93f@mail.gmail.com> In-Reply-To: <487CA8DC.2090703@FreeBSD.org> References: <20def4870807140902y4e5aad69r649d577fb5f5ad84@mail.gmail.com> <487BE91E.1020202@FreeBSD.org> <20def4870807150605w6e3de82eq4a999360e9b49b6c@mail.gmail.com> <487CA8DC.2090703@FreeBSD.org>
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>
>
> Something is still unclear. All my locks are MTX_DEF type, which means
>> sleepable, including the one specified in the crash report (MTNIC state
>> semaphore).
>> This crash happens when I try to call bus_resource_alloc_any for a SYS_REQ
>> which is trying to obtain the second lock (ACPI root bus). How come my
>> MTX_DEF lock is being treated as as non-sleepable?
>>
>
> MTX_DEF locks *are* non-sleepable :-)
>
> Kris
>
Good news :-)
Yet the documentation is confusing me:
man pages say:
MTX_DEF Default mutexes will always allow the current thread to be
suspended to avoid deadlock conditions against interrupt
threads. The implementation of this lock type may spin
for a while before suspending the current thread.
and in mutex.h:
/*
* Mutex types and options passed to mtx_init(). MTX_QUIET and MTX_DUPOK
* can also be passed in.
*/
#define MTX_DEF 0x00000000 /* DEFAULT (sleep) lock */
#define MTX_SPIN 0x00000001 /* Spin lock (disables interrupts) */
#define MTX_RECURSE 0x00000004 /* Option: lock allowed to recurse */
#define MTX_NOWITNESS 0x00000008 /* Don't do any witness checking. */
#define MTX_NOPROFILE 0x00000020 /* Don't profile this lock */
What does the "DEFAULT (sleep) lock" comment near MTX_DEF means?
And which ones are sleepable?.. I guess I'm missing something here.
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