Date: Thu, 9 Feb 2023 16:02:46 GMT From: Mitchell Horne <mhorne@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 1029dab63457 - main - mi_switch(): clean up switch types and their usage Message-ID: <202302091602.319G2kuC094744@gitrepo.freebsd.org>
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The branch main has been updated by mhorne: URL: https://cgit.FreeBSD.org/src/commit/?id=1029dab63457f23dace4dab3b698f1c177939b93 commit 1029dab63457f23dace4dab3b698f1c177939b93 Author: Mitchell Horne <mhorne@FreeBSD.org> AuthorDate: 2023-02-09 15:40:29 +0000 Commit: Mitchell Horne <mhorne@FreeBSD.org> CommitDate: 2023-02-09 16:01:32 +0000 mi_switch(): clean up switch types and their usage Overall, this is a non-functional change, except for kernels built with SCHED_STATS. However, the switch types are useful for communicating the intent of the caller. 1. Ensure that every caller provides a type. In most cases, we upgrade the basic yield to sched_relinquish() aka SWT_RELINQUISH. 2. The case of sched_bind() is distinct, so add a new switch type SWT_BIND. 3. Remove the two unused types, SWT_PREEMPT and SWT_SLEEPQTIMO. 4. Remove SWT_NONE altogether and assert that callers always provide a type flag. 5. Reference the mi_switch(9) man page in the comments, as these flags will be documented there. Reviewed by: kib, markj Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D38184 --- sys/dev/dpaa/bman_portals.c | 3 +-- sys/dev/dpaa/qman_portals.c | 3 +-- sys/kern/kern_poll.c | 3 +-- sys/kern/kern_switch.c | 12 ++++-------- sys/kern/kern_synch.c | 9 +++++++-- sys/kern/sched_4bsd.c | 2 +- sys/kern/sched_ule.c | 2 +- sys/kern/vfs_bio.c | 4 ++-- sys/sys/proc.h | 28 +++++++++++++--------------- 9 files changed, 31 insertions(+), 35 deletions(-) diff --git a/sys/dev/dpaa/bman_portals.c b/sys/dev/dpaa/bman_portals.c index 9ef2bf7aa61c..d3c027bb29f8 100644 --- a/sys/dev/dpaa/bman_portals.c +++ b/sys/dev/dpaa/bman_portals.c @@ -141,8 +141,7 @@ bman_portal_setup(struct bman_softc *bsc) } /* Not inititialized and "owned" by another thread */ - thread_lock(curthread); - mi_switch(SW_VOL); + sched_relinquish(curthread); } /* Map portal registers */ diff --git a/sys/dev/dpaa/qman_portals.c b/sys/dev/dpaa/qman_portals.c index 92461665def2..37f9b4eec178 100644 --- a/sys/dev/dpaa/qman_portals.c +++ b/sys/dev/dpaa/qman_portals.c @@ -146,8 +146,7 @@ qman_portal_setup(struct qman_softc *qsc) } /* Not inititialized and "owned" by another thread */ - thread_lock(curthread); - mi_switch(SW_VOL); + sched_relinquish(curthread); } /* Map portal registers */ diff --git a/sys/kern/kern_poll.c b/sys/kern/kern_poll.c index 8232f98f59ef..64deb7132710 100644 --- a/sys/kern/kern_poll.c +++ b/sys/kern/kern_poll.c @@ -565,8 +565,7 @@ poll_idle(void) if (poll_in_idle_loop && poll_handlers > 0) { idlepoll_sleeping = 0; ether_poll(poll_each_burst); - thread_lock(td); - mi_switch(SW_VOL); + sched_relinquish(td); } else { idlepoll_sleeping = 1; tsleep(&idlepoll_sleeping, 0, "pollid", hz * 3); diff --git a/sys/kern/kern_switch.c b/sys/kern/kern_switch.c index 9d48ab188e13..aee0c9cbd1ae 100644 --- a/sys/kern/kern_switch.c +++ b/sys/kern/kern_switch.c @@ -83,25 +83,19 @@ SYSCTL_INT(_kern_sched, OID_AUTO, preemption, CTLFLAG_RD, SYSCTL_NODE(_kern_sched, OID_AUTO, stats, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, "switch stats"); -/* Switch reasons from mi_switch(). */ +/* Switch reasons from mi_switch(9). */ DPCPU_DEFINE(long, sched_switch_stats[SWT_COUNT]); -SCHED_STAT_DEFINE_VAR(uncategorized, - &DPCPU_NAME(sched_switch_stats[SWT_NONE]), ""); -SCHED_STAT_DEFINE_VAR(preempt, - &DPCPU_NAME(sched_switch_stats[SWT_PREEMPT]), ""); SCHED_STAT_DEFINE_VAR(owepreempt, &DPCPU_NAME(sched_switch_stats[SWT_OWEPREEMPT]), ""); SCHED_STAT_DEFINE_VAR(turnstile, &DPCPU_NAME(sched_switch_stats[SWT_TURNSTILE]), ""); SCHED_STAT_DEFINE_VAR(sleepq, &DPCPU_NAME(sched_switch_stats[SWT_SLEEPQ]), ""); -SCHED_STAT_DEFINE_VAR(sleepqtimo, - &DPCPU_NAME(sched_switch_stats[SWT_SLEEPQTIMO]), ""); SCHED_STAT_DEFINE_VAR(relinquish, &DPCPU_NAME(sched_switch_stats[SWT_RELINQUISH]), ""); SCHED_STAT_DEFINE_VAR(needresched, &DPCPU_NAME(sched_switch_stats[SWT_NEEDRESCHED]), ""); -SCHED_STAT_DEFINE_VAR(idle, +SCHED_STAT_DEFINE_VAR(idle, &DPCPU_NAME(sched_switch_stats[SWT_IDLE]), ""); SCHED_STAT_DEFINE_VAR(iwait, &DPCPU_NAME(sched_switch_stats[SWT_IWAIT]), ""); @@ -111,6 +105,8 @@ SCHED_STAT_DEFINE_VAR(remotepreempt, &DPCPU_NAME(sched_switch_stats[SWT_REMOTEPREEMPT]), ""); SCHED_STAT_DEFINE_VAR(remotewakeidle, &DPCPU_NAME(sched_switch_stats[SWT_REMOTEWAKEIDLE]), ""); +SCHED_STAT_DEFINE_VAR(bind, + &DPCPU_NAME(sched_switch_stats[SWT_BIND]), ""); static int sysctl_stats_reset(SYSCTL_HANDLER_ARGS) diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c index 7d0cb6178fc3..63a78353e9a5 100644 --- a/sys/kern/kern_synch.c +++ b/sys/kern/kern_synch.c @@ -483,7 +483,7 @@ kdb_switch(void) } /* - * The machine independent parts of context switching. + * mi_switch(9): The machine-independent parts of context switching. * * The thread lock is required on entry and is no longer held on return. */ @@ -500,10 +500,15 @@ mi_switch(int flags) if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) mtx_assert(&Giant, MA_NOTOWNED); #endif + /* thread_lock() performs spinlock_enter(). */ KASSERT(td->td_critnest == 1 || KERNEL_PANICKED(), - ("mi_switch: switch in a critical section")); + ("mi_switch: switch in a critical section")); KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, ("mi_switch: switch must be voluntary or involuntary")); + KASSERT((flags & SW_TYPE_MASK) != 0, + ("mi_switch: a switch reason (type) must be specified")); + KASSERT((flags & SW_TYPE_MASK) < SWT_COUNT, + ("mi_switch: invalid switch reason %d", (flags & SW_TYPE_MASK))); /* * Don't perform context switches from the debugger. diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c index f0da4f8d8496..e81b0c9d46ec 100644 --- a/sys/kern/sched_4bsd.c +++ b/sys/kern/sched_4bsd.c @@ -1582,7 +1582,7 @@ sched_bind(struct thread *td, int cpu) if (PCPU_GET(cpuid) == cpu) return; - mi_switch(SW_VOL); + mi_switch(SW_VOL | SWT_BIND); thread_lock(td); #endif } diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c index ba179caf5d34..881413ca5e73 100644 --- a/sys/kern/sched_ule.c +++ b/sys/kern/sched_ule.c @@ -2922,7 +2922,7 @@ sched_bind(struct thread *td, int cpu) return; ts->ts_cpu = cpu; /* When we return from mi_switch we'll be on the correct cpu. */ - mi_switch(SW_VOL); + mi_switch(SW_VOL | SWT_BIND); thread_lock(td); } diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c index cb94f3390d8a..3a5afec88a02 100644 --- a/sys/kern/vfs_bio.c +++ b/sys/kern/vfs_bio.c @@ -72,6 +72,7 @@ __FBSDID("$FreeBSD$"); #include <sys/refcount.h> #include <sys/resourcevar.h> #include <sys/rwlock.h> +#include <sys/sched.h> #include <sys/smp.h> #include <sys/sysctl.h> #include <sys/syscallsubr.h> @@ -1425,8 +1426,7 @@ bufshutdown(int show_busybufs) * threads to run. */ for (subiter = 0; subiter < 50 * iter; subiter++) { - thread_lock(curthread); - mi_switch(SW_VOL); + sched_relinquish(curthread); DELAY(1000); } #endif diff --git a/sys/sys/proc.h b/sys/sys/proc.h index d031c2a73ce6..c6670bdc96f8 100644 --- a/sys/sys/proc.h +++ b/sys/sys/proc.h @@ -904,22 +904,20 @@ struct proc { #ifdef _KERNEL -/* Types and flags for mi_switch(). */ +/* Types and flags for mi_switch(9). */ #define SW_TYPE_MASK 0xff /* First 8 bits are switch type */ -#define SWT_NONE 0 /* Unspecified switch. */ -#define SWT_PREEMPT 1 /* Switching due to preemption. */ -#define SWT_OWEPREEMPT 2 /* Switching due to owepreempt. */ -#define SWT_TURNSTILE 3 /* Turnstile contention. */ -#define SWT_SLEEPQ 4 /* Sleepq wait. */ -#define SWT_SLEEPQTIMO 5 /* Sleepq timeout wait. */ -#define SWT_RELINQUISH 6 /* yield call. */ -#define SWT_NEEDRESCHED 7 /* NEEDRESCHED was set. */ -#define SWT_IDLE 8 /* Switching from the idle thread. */ -#define SWT_IWAIT 9 /* Waiting for interrupts. */ -#define SWT_SUSPEND 10 /* Thread suspended. */ -#define SWT_REMOTEPREEMPT 11 /* Remote processor preempted. */ -#define SWT_REMOTEWAKEIDLE 12 /* Remote processor preempted idle. */ -#define SWT_COUNT 13 /* Number of switch types. */ +#define SWT_OWEPREEMPT 1 /* Switching due to owepreempt. */ +#define SWT_TURNSTILE 2 /* Turnstile contention. */ +#define SWT_SLEEPQ 3 /* Sleepq wait. */ +#define SWT_RELINQUISH 4 /* yield call. */ +#define SWT_NEEDRESCHED 5 /* NEEDRESCHED was set. */ +#define SWT_IDLE 6 /* Switching from the idle thread. */ +#define SWT_IWAIT 7 /* Waiting for interrupts. */ +#define SWT_SUSPEND 8 /* Thread suspended. */ +#define SWT_REMOTEPREEMPT 9 /* Remote processor preempted. */ +#define SWT_REMOTEWAKEIDLE 10 /* Remote processor preempted idle. */ +#define SWT_BIND 11 /* Thread bound to a new CPU. */ +#define SWT_COUNT 12 /* Number of switch types. */ /* Flags */ #define SW_VOL 0x0100 /* Voluntary switch. */ #define SW_INVOL 0x0200 /* Involuntary switch. */
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