On Wed, Aug 11, 2010 at 01:21:46PM +0200, Attilio Rao wrote: > 2010/8/11 Kostik Belousov <kostik...@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: > >> IPI handlers may run generally with interrupts disabled because they > >> are served via an interrupt gate. > >> > >> However, that doesn't explicitly prevent preemption and thread > >> migration thus scheduler pinning may be necessary in some handlers. > >> Fix that. > > > > How the preemption is supposed to happen ? Aside from the explicit > > calls to mi_switch() from e.g. critical_exit(). > > 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 = PCPU_GET(cpuid);
cpumask = PCPU_GET(cpumask);
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