Date: Fri, 27 Aug 2010 01:10:41 +0300 From: Andriy Gapon <avg@icyb.net.ua> To: mdf@FreeBSD.org Cc: freebsd-current@FreeBSD.org Subject: Re: sched_pin() bug in SCHED_ULE Message-ID: <4C76E661.60600@icyb.net.ua> In-Reply-To: <AANLkTi=7cLfH3h3jMVhbEzNsuiPod3Zx=PiazK7Dn4%2BA@mail.gmail.com> References: <AANLkTin6V9pc3d7ifyOmR2V-H5-g_AQFji-LbZzWfAKM@mail.gmail.com> <201008261649.20543.jhb@freebsd.org> <AANLkTi=7cLfH3h3jMVhbEzNsuiPod3Zx=PiazK7Dn4%2BA@mail.gmail.com>
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on 27/08/2010 00:20 mdf@FreeBSD.org said the following: > > I tried making sched_pin() a real function which used > intr_disable/intr_restore around saving off td->td_oncpu, > td->td_lastcpu and ts->ts_cpu, and the stack at the time of call. In > sched_switch when I saw an unexpected migration I printed all that > out. I found that on my boxes, at sched_pin() time ts_cpu was already > different from td->td_oncpu, so the specific problem I was having was > that while another thread can change ts_cpu it has no way to force > that thread to immediately migrate. Like e.g. in sched_affinity where ts_cpu is first changed and then the old cpu is ipi-ed? > I believe the below patch fixes the issue, though I'm open to other methods: > > > Index: kern/sched_ule.c > =================================================================== > --- kern/sched_ule.c (.../head/src/sys) (revision 158279) > +++ kern/sched_ule.c (.../branches/BR_BUG_67957/src/sys) (revision 158279) > @@ -112,6 +112,7 @@ > /* flags kept in ts_flags */ > #define TSF_BOUND 0x0001 /* Thread can not migrate. */ > #define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */ > +#define TSF_BINDING 0x0004 /* Thread is being bound. */ I don't really follow why TSF_BINDING is needed, i.e. why TSF_BOUND is not sufficient in this case? -- Andriy Gapon
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