Date: Wed, 11 Aug 2010 15:34:30 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Attilio Rao <attilio@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r211176 - in head/sys: amd64/amd64 i386/i386 Message-ID: <20100811123430.GK2396@deviant.kiev.zoral.com.ua> In-Reply-To: <AANLkTikk3m-=5W7TVV5C-XM4AnwS1LuAi7GGEeP0B9dV@mail.gmail.com> References: <201008111051.o7BApRp4028538@svn.freebsd.org> <20100811105739.GJ2396@deviant.kiev.zoral.com.ua> <AANLkTikk3m-=5W7TVV5C-XM4AnwS1LuAi7GGEeP0B9dV@mail.gmail.com>
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--STPqjqpCrtky8aYs Content-Type: text/plain; charset=koi8-r Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Aug 11, 2010 at 01:21:46PM +0200, Attilio Rao wrote: > 2010/8/11 Kostik Belousov <kostikbel@gmail.com>: > > On Wed, Aug 11, 2010 at 10:51:27AM +0000, Attilio Rao wrote: > >> Author: attilio > >> Date: Wed Aug 11 10:51:27 2010 > >> New Revision: 211176 > >> URL: http://svn.freebsd.org/changeset/base/211176 > >> > >> Log: > >> =9A IPI handlers may run generally with interrupts disabled because th= ey > >> =9A are served via an interrupt gate. > >> > >> =9A However, that doesn't explicitly prevent preemption and thread > >> =9A migration thus scheduler pinning may be necessary in some handlers. > >> =9A Fix that. > > > > How the preemption is supposed to happen ? Aside from the explicit > > calls to mi_switch() from e.g. critical_exit(). >=20 > IIRC it should be hardclock() willing to schedule the softclock(). It > is the critical_exit() in the thread_unlock() that may trigger it > (sorry for not digging more, it was a while back that I hacked this > part, but I guess you can verify on your own). > We already have other points within the kernel that take care of > dealing with preemption/migration like lapic_handle_timer(), for > example. Right, and if the interrupts are indeed disabled, I do not see how the preemption may be triggered in the fragments like cpu =3D PCPU_GET(cpuid); cpumask =3D PCPU_GET(cpumask); --STPqjqpCrtky8aYs Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkximNYACgkQC3+MBN1Mb4hokwCfVKvpntMv62suh6fSzcoc3jfY Q9sAoJiLrEVzHRQAc/enXp5bNnNPGlnK =OPog -----END PGP SIGNATURE----- --STPqjqpCrtky8aYs--
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