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Create a separate kthread that executes sched_cpu() once a second. Because

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sched_cpu() locks an sx lock (allproc_lock) which can sleep if it fails to
acquire the lock, it is not safe to execute this in a callout handler from
softclock().
This commit is contained in:
John Baldwin 2003-12-26 17:07:29 +00:00
parent 2df3425140
commit c55bbb6cb7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=123871
1 changed files with 21 additions and 6 deletions
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27
sys/kern/sched_4bsd.c
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@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/kthread.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
@ -80,11 +81,11 @@ struct td_sched *thread0_sched = NULL;
static int sched_quantum; /* Roundrobin scheduling quantum in ticks. */
#define SCHED_QUANTUM (hz / 10) /* Default sched quantum */
static struct callout schedcpu_callout;
static struct callout roundrobin_callout;
static void roundrobin(void *arg);
static void schedcpu(void *arg);
static void schedcpu(void);
static void schedcpu_thread(void *dummy);
static void sched_setup(void *dummy);
static void maybe_resched(struct thread *td);
static void updatepri(struct ksegrp *kg);
@ -244,7 +245,7 @@ SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
*/
/* ARGSUSED */
static void
schedcpu(void *arg)
schedcpu(void)
{
register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
struct thread *td;
@ -348,7 +349,20 @@ schedcpu(void *arg)
mtx_unlock_spin(&sched_lock);
} /* end of process loop */
sx_sunlock(&allproc_lock);
callout_reset(&schedcpu_callout, hz, schedcpu, NULL);
}
/*
* Main loop for a kthread that executes schedcpu once a second.
*/
static void
schedcpu_thread(void *dummy)
{
int nowake;
for (;;) {
schedcpu();
tsleep(&nowake, curthread->td_priority, "-", hz);
}
}
/*
@ -407,12 +421,13 @@ sched_setup(void *dummy)
sched_quantum = SCHED_QUANTUM;
hogticks = 2 * sched_quantum;
callout_init(&schedcpu_callout, CALLOUT_MPSAFE);
callout_init(&roundrobin_callout, 0);
/* Kick off timeout driven events by calling first time. */
roundrobin(NULL);
schedcpu(NULL);
/* Kick off schedcpu kernel process. */
kthread_create(schedcpu_thread, NULL, NULL, 0, 0, "schedcpu");
}
/* External interfaces start here */