> Date: Mon, 10 Jul 2023 09:57:39 -0500 > From: Scott Cheloha <scottchel...@gmail.com> > > On Mon, Jul 10, 2023 at 07:42:55AM -0600, Theo de Raadt wrote: > > I dare you to write the simplest fix for this, instead of a diff that > > scrolls by. > > This patch seems to work. Will need to bang on it for a few more days. > > 1. Disable gmoninit after sched_stop_scondary_cpus(). The secondary > CPUs have halted, so we aren't racing sysctl(2) on a secondary CPU. > > 2. Restore gmoninit between resume_mp() and sched_start_secondary_cpus(). > The secondary CPUs are out of cpu_hatch(), which is probably where we > are crashing during resume. The secondary CPUs haven't started > scheduling yet, so we aren't racing sysctl(2).
It is still a bit scary to have cpu_hatch() call _mcount() but I guess adding __attribute__((no_profile)) to all of the functions called by cpu_hatch() isn't really workable either. That said... > Index: subr_suspend.c > =================================================================== > RCS file: /cvs/src/sys/kern/subr_suspend.c,v > retrieving revision 1.15 > diff -u -p -r1.15 subr_suspend.c > --- subr_suspend.c 2 Jul 2023 19:02:27 -0000 1.15 > +++ subr_suspend.c 10 Jul 2023 14:51:01 -0000 > @@ -18,6 +18,7 @@ > > #include <sys/param.h> > #include <sys/systm.h> > +#include <sys/atomic.h> > #include <sys/buf.h> > #include <sys/clockintr.h> > #include <sys/reboot.h> > @@ -100,6 +101,14 @@ top: > #ifdef MULTIPROCESSOR > sched_stop_secondary_cpus(); > KASSERT(CPU_IS_PRIMARY(curcpu())); > +#endif > +#ifdef GPROF > + extern int gmoninit; > + int gmon_state = gmoninit; No variable declarations in the middle of functions please. > + gmoninit = 0; > + membar_producer(); Why are you messing with memory barriers here? > +#endif > +#ifdef MULTIPROCESSOR > sleep_mp(); > #endif > > @@ -172,6 +181,12 @@ fail_suspend: > resume_randomness(rndbuf, rndbuflen); > #ifdef MULTIPROCESSOR > resume_mp(); > +#endif > +#ifdef GPROF > + gmoninit = gmon_state; > + membar_producer(); And here? > +#endif > +#ifdef MULTIPROCESSOR > sched_start_secondary_cpus(); > #endif > vfs_stall(curproc, 0); >
