Date: Wed, 19 Apr 2017 17:36:52 +0000 From: "Somayajulu, David" <David.Somayajulu@cavium.com> To: Hans Petter Selasky <hps@selasky.org>, Sepherosa Ziehau <sepherosa@gmail.com> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: RE: Question on taskqueue_drain Message-ID: <BY2PR07MB1474DA5E249A0FE4CEFDA0A7EE180@BY2PR07MB1474.namprd07.prod.outlook.com> In-Reply-To: <1fb80f2b-9086-0260-2f63-bdaf8afc1c4c@selasky.org> References: <BY2PR07MB14745123AC235B06BCD2987DEE190@BY2PR07MB1474.namprd07.prod.outlook.com> <BY2PR07MB1474C78A241A7CA1F2396435EE180@BY2PR07MB1474.namprd07.prod.outlook.com> <CAMOc5cxtSakeBhskbmfW4BxsbgdRDp22AVBYrDgReCP91YLY7g@mail.gmail.com> <1fb80f2b-9086-0260-2f63-bdaf8afc1c4c@selasky.org>
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Hans, Thanks for the info. > No sleeping functions like taskqueue_drain() can be called when the MTX_D= EF lock is grabbed. I am guessing this is true irrespective of whether the taskqueue is "fast" = or not. Thanks David S. -----Original Message----- From: Hans Petter Selasky [mailto:hps@selasky.org]=20 Sent: Tuesday, April 18, 2017 9:22 PM To: Sepherosa Ziehau <sepherosa@gmail.com>; Somayajulu, David <David.Somaya= julu@cavium.com> Cc: freebsd-net@freebsd.org Subject: Re: Question on taskqueue_drain On 04/19/17 05:37, Sepherosa Ziehau wrote: > On Wed, Apr 19, 2017 at 10:39 AM, Somayajulu, David=20 > <David.Somayajulu@cavium.com> wrote: >> Sorry what I meant to ask was, whether it is O.K to call taskqueue_drain= (), when an MTX_DEF lock is grabbed prior to calling taskqueue_drain(). >> > > You will hit WITNESS, if the drain needs to wait; that's probably the=20 > best case. If the lock will be acquired in the task being drained,=20 > this leads to deadlock. > Hi, No sleeping functions like taskqueue_drain() can be called when the MTX_DEF= lock is grabbed. --HPS
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