From de29a8a57bd877d26efe375510c0b3c2aded54f9 Mon Sep 17 00:00:00 2001 From: claudio Date: Wed, 29 May 2024 18:55:45 +0000 Subject: [PATCH] Convert SCHED_LOCK from a recursive kernel lock to a mutex. Over the last weeks the last SCHED_LOCK recursion was removed so this is now possible and will allow to split up the SCHED_LOCK in a upcoming step. Instead of implementing an MP and SP version of SCHED_LOCK this just always uses the mutex implementation. While this makes the local s argument unused (the spl is now tracked by the mutex itself) it is still there to keep this diff minimal. Tested by many. OK jca@ mpi@ --- sys/kern/kern_fork.c | 8 ++------ sys/kern/kern_lock.c | 5 +---- sys/kern/sched_bsd.c | 28 +++++++++++----------------- sys/sys/sched.h | 40 +++++++++------------------------------- 4 files changed, 23 insertions(+), 58 deletions(-) diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c index 1cfb84d092b..3ed90a60388 100644 --- a/sys/kern/kern_fork.c +++ b/sys/kern/kern_fork.c @@ -1,4 +1,4 @@ -/* $OpenBSD: kern_fork.c,v 1.258 2024/05/20 10:32:20 claudio Exp $ */ +/* $OpenBSD: kern_fork.c,v 1.259 2024/05/29 18:55:45 claudio Exp $ */ /* $NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $ */ /* @@ -688,12 +688,8 @@ proc_trampoline_mi(void) struct proc *p = curproc; SCHED_ASSERT_LOCKED(); - clear_resched(curcpu()); - -#if defined(MULTIPROCESSOR) - __mp_unlock(&sched_lock); -#endif + mtx_leave(&sched_lock); spl0(); SCHED_ASSERT_UNLOCKED(); diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c index 19f441bd5ce..fb38210927d 100644 --- a/sys/kern/kern_lock.c +++ b/sys/kern/kern_lock.c @@ -1,4 +1,4 @@ -/* $OpenBSD: kern_lock.c,v 1.73 2024/03/26 18:18:30 bluhm Exp $ */ +/* $OpenBSD: kern_lock.c,v 1.74 2024/05/29 18:55:45 claudio Exp $ */ /* * Copyright (c) 2017 Visa Hankala @@ -97,9 +97,6 @@ ___mp_lock_init(struct __mp_lock *mpl, const struct lock_type *type) if (mpl == &kernel_lock) mpl->mpl_lock_obj.lo_flags = LO_WITNESS | LO_INITIALIZED | LO_SLEEPABLE | (LO_CLASS_KERNEL_LOCK << LO_CLASSSHIFT); - else if (mpl == &sched_lock) - mpl->mpl_lock_obj.lo_flags = LO_WITNESS | LO_INITIALIZED | - LO_RECURSABLE | (LO_CLASS_SCHED_LOCK << LO_CLASSSHIFT); WITNESS_INIT(&mpl->mpl_lock_obj, type); #endif } diff --git a/sys/kern/sched_bsd.c b/sys/kern/sched_bsd.c index 25b221c1ee2..1cfd32746f0 100644 --- a/sys/kern/sched_bsd.c +++ b/sys/kern/sched_bsd.c @@ -1,4 +1,4 @@ -/* $OpenBSD: sched_bsd.c,v 1.91 2024/03/30 13:33:20 mpi Exp $ */ +/* $OpenBSD: sched_bsd.c,v 1.92 2024/05/29 18:55:45 claudio Exp $ */ /* $NetBSD: kern_synch.c,v 1.37 1996/04/22 01:38:37 christos Exp $ */ /*- @@ -57,9 +57,7 @@ uint64_t roundrobin_period; /* [I] roundrobin period (ns) */ int lbolt; /* once a second sleep address */ -#ifdef MULTIPROCESSOR -struct __mp_lock sched_lock; -#endif +struct mutex sched_lock; void update_loadavg(void *); void schedcpu(void *); @@ -351,12 +349,11 @@ mi_switch(void) struct proc *nextproc; struct process *pr = p->p_p; struct timespec ts; + int oldipl, s; #ifdef MULTIPROCESSOR int hold_count; - int sched_count; #endif - assertwaitok(); KASSERT(p->p_stat != SONPROC); SCHED_ASSERT_LOCKED(); @@ -365,7 +362,6 @@ mi_switch(void) /* * Release the kernel_lock, as we are about to yield the CPU. */ - sched_count = __mp_release_all_but_one(&sched_lock); if (_kernel_lock_held()) hold_count = __mp_release_all(&kernel_lock); else @@ -411,6 +407,9 @@ mi_switch(void) nextproc = sched_chooseproc(); + /* preserve old IPL level so we can switch back to that */ + oldipl = MUTEX_OLDIPL(&sched_lock); + if (p != nextproc) { uvmexp.swtch++; TRACEPOINT(sched, off__cpu, nextproc->p_tid + THREAD_PID_OFFSET, @@ -426,18 +425,13 @@ mi_switch(void) SCHED_ASSERT_LOCKED(); - /* - * To preserve lock ordering, we need to release the sched lock - * and grab it after we grab the big lock. - * In the future, when the sched lock isn't recursive, we'll - * just release it here. - */ -#ifdef MULTIPROCESSOR - __mp_unlock(&sched_lock); -#endif + /* Restore proc's IPL. */ + MUTEX_OLDIPL(&sched_lock) = oldipl; + SCHED_UNLOCK(s); SCHED_ASSERT_UNLOCKED(); + assertwaitok(); smr_idle(); /* @@ -468,8 +462,8 @@ mi_switch(void) */ if (hold_count) __mp_acquire_count(&kernel_lock, hold_count); - __mp_acquire_count(&sched_lock, sched_count + 1); #endif + SCHED_LOCK(s); } /* diff --git a/sys/sys/sched.h b/sys/sys/sched.h index ac6dad2a8bb..593bd3e60ae 100644 --- a/sys/sys/sched.h +++ b/sys/sys/sched.h @@ -1,4 +1,4 @@ -/* $OpenBSD: sched.h,v 1.70 2024/01/24 19:23:38 cheloha Exp $ */ +/* $OpenBSD: sched.h,v 1.71 2024/05/29 18:55:45 claudio Exp $ */ /* $NetBSD: sched.h,v 1.2 1999/02/28 18:14:58 ross Exp $ */ /*- @@ -199,52 +199,30 @@ void remrunqueue(struct proc *); func(); \ } while (0) -#if defined(MULTIPROCESSOR) -#include - -/* - * XXX Instead of using struct lock for the kernel lock and thus requiring us - * XXX to implement simplelocks, causing all sorts of fine-grained locks all - * XXX over our tree to be activated, the sched_lock is a different kind of - * XXX lock to avoid introducing locking protocol bugs. - */ -extern struct __mp_lock sched_lock; +extern struct mutex sched_lock; #define SCHED_ASSERT_LOCKED() \ do { \ - splassert(IPL_SCHED); \ - KASSERT(__mp_lock_held(&sched_lock, curcpu())); \ + MUTEX_ASSERT_LOCKED(&sched_lock); \ } while (0) #define SCHED_ASSERT_UNLOCKED() \ do { \ - KASSERT(__mp_lock_held(&sched_lock, curcpu()) == 0); \ + MUTEX_ASSERT_UNLOCKED(&sched_lock); \ } while (0) -#define SCHED_LOCK_INIT() __mp_lock_init(&sched_lock) +#define SCHED_LOCK_INIT() mtx_init(&sched_lock, IPL_SCHED) #define SCHED_LOCK(s) \ do { \ - s = splsched(); \ - __mp_lock(&sched_lock); \ + (s) = 0; /* XXX cleanup useless argument */ \ + mtx_enter(&sched_lock); \ } while (/* CONSTCOND */ 0) #define SCHED_UNLOCK(s) \ do { \ - __mp_unlock(&sched_lock); \ - splx(s); \ + (void)s; /* XXX cleanup useless argument */ \ + mtx_leave(&sched_lock); \ } while (/* CONSTCOND */ 0) -#else /* ! MULTIPROCESSOR */ - -#define SCHED_ASSERT_LOCKED() splassert(IPL_SCHED); -#define SCHED_ASSERT_UNLOCKED() /* nothing */ - -#define SCHED_LOCK_INIT() /* nothing */ - -#define SCHED_LOCK(s) s = splsched() -#define SCHED_UNLOCK(s) splx(s) - -#endif /* MULTIPROCESSOR */ - #endif /* _KERNEL */ #endif /* _SYS_SCHED_H_ */ -- 2.20.1