Date: Sun, 09 Sep 2012 15:15:44 -0400 From: John Baldwin <jhb@FreeBSD.org> To: attilio@FreeBSD.org Cc: Konstantin Belousov <kostikbel@gmail.com>, Davide Italiano <davide@freebsd.org>, src-committers@freebsd.org, svn-src-projects@freebsd.org Subject: Re: svn commit: r238907 - projects/calloutng/sys/kern Message-ID: <504CEAE0.704@FreeBSD.org> In-Reply-To: <CAJ-FndARWZGwdiLeaQcnM%2BM%2Bm8zmBLuMrTkgoCFeesXPR=08pA@mail.gmail.com> References: <201207301350.q6UDobCI099069@svn.freebsd.org> <CAJ-FndBj8tpC_BJXs_RH8sG2TBG8yA=Lxu3-GTVT9Ap_zOCuVQ@mail.gmail.com> <CAJ-FndDnO7wjnWPV0tTu%2BUGHjsxa3YDarMxmyei3ZmjLAFvRkQ@mail.gmail.com> <201207301732.33474.jhb@freebsd.org> <CAJ-FndD5EO12xsWOAe6u0EvX00q33wxO4OivnGjzj0=T2Oe8uA@mail.gmail.com> <CAJ-FndARWZGwdiLeaQcnM%2BM%2Bm8zmBLuMrTkgoCFeesXPR=08pA@mail.gmail.com>
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On 9/9/12 11:03 AM, Attilio Rao wrote:
> On 8/2/12, Attilio Rao <attilio@freebsd.org> wrote:
>> On 7/30/12, John Baldwin <jhb@freebsd.org> wrote:
>
> [ trimm ]
>
>>> --- //depot/projects/smpng/sys/kern/subr_turnstile.c 2012-06-04
>>> 18:27:32.000000000 0000
>>> +++ //depot/user/jhb/lock/kern/subr_turnstile.c 2012-06-05
>>> 00:27:57.000000000 0000
>>> @@ -684,6 +684,7 @@
>>> if (owner)
>>> MPASS(owner->td_proc->p_magic == P_MAGIC);
>>> MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
>>> + KASSERT(!TD_IS_IDLETHREAD(td), ("idle threads cannot block on locks"));
>>>
>>> /*
>>> * If the lock does not already have a turnstile, use this thread's
>>
>> I'm wondering if we should also use similar checks in places doing
>> adaptive spinning (including the TD_NO_SLEEPING check). Likely yes.
>
> So what do you think about this?
This is isn't really good enough then. An idle thread should not
acquire any lock that isn't a spin lock. Instead, you would be
better off removing the assert I added above and adding an assert to
mtx_lock(), rw_{rw}lock(), sx_{sx}lock(), lockmgr(), rm_{rw}lock() and
all the try variants of those.
--
John Baldwin
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