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remove stop_scheduler_on_panic knob

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There has not been any complaints about the default behavior, so there
is no need to keep a knob that enables the worse alternative.

Now that the hard-stopping of other CPUs is the only behavior, the panic_cpu
spinlock-like logic can be dropped, because only a single CPU is
supposed to win stop_cpus_hard(other_cpus) race and proceed past that
call.

MFC after:	1 month
This commit is contained in:
Andriy Gapon 2012-11-25 14:22:08 +00:00
parent 64ad6bf196
commit 6898bee9a9
1 changed files with 16 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
sys/kern/kern_shutdown.c
View File

@ -121,11 +121,6 @@ SYSCTL_INT(_kern, OID_AUTO, sync_on_panic, CTLFLAG_RW | CTLFLAG_TUN,
&sync_on_panic, 0, "Do a sync before rebooting from a panic");
TUNABLE_INT("kern.sync_on_panic", &sync_on_panic);
static int stop_scheduler_on_panic = 1;
SYSCTL_INT(_kern, OID_AUTO, stop_scheduler_on_panic, CTLFLAG_RW | CTLFLAG_TUN,
&stop_scheduler_on_panic, 0, "stop scheduler upon entering panic");
TUNABLE_INT("kern.stop_scheduler_on_panic", &stop_scheduler_on_panic);
static SYSCTL_NODE(_kern, OID_AUTO, shutdown, CTLFLAG_RW, 0,
"Shutdown environment");
@ -552,7 +547,6 @@ void
panic(const char *fmt, ...)
{
#ifdef SMP
static volatile u_int panic_cpu = NOCPU;
cpuset_t other_cpus;
#endif
struct thread *td = curthread;
@ -560,39 +554,27 @@ panic(const char *fmt, ...)
va_list ap;
static char buf[256];
if (stop_scheduler_on_panic)
spinlock_enter();
else
critical_enter();
spinlock_enter();
#ifdef SMP
/*
* We don't want multiple CPU's to panic at the same time, so we
* use panic_cpu as a simple spinlock. We have to keep checking
* panic_cpu if we are spinning in case the panic on the first
* CPU is canceled.
* stop_cpus_hard(other_cpus) should prevent multiple CPUs from
* concurrently entering panic. Only the winner will proceed
* further.
*/
if (panic_cpu != PCPU_GET(cpuid))
while (atomic_cmpset_int(&panic_cpu, NOCPU,
PCPU_GET(cpuid)) == 0)
while (panic_cpu != NOCPU)
; /* nothing */
if (stop_scheduler_on_panic) {
if (panicstr == NULL && !kdb_active) {
other_cpus = all_cpus;
CPU_CLR(PCPU_GET(cpuid), &other_cpus);
stop_cpus_hard(other_cpus);
}
/*
* We set stop_scheduler here and not in the block above,
* because we want to ensure that if panic has been called and
* stop_scheduler_on_panic is true, then stop_scheduler will
* always be set. Even if panic has been entered from kdb.
*/
td->td_stopsched = 1;
if (panicstr == NULL && !kdb_active) {
other_cpus = all_cpus;
CPU_CLR(PCPU_GET(cpuid), &other_cpus);
stop_cpus_hard(other_cpus);
}
/*
* We set stop_scheduler here and not in the block above,
* because we want to ensure that if panic has been called and
* stop_scheduler_on_panic is true, then stop_scheduler will
* always be set. Even if panic has been entered from kdb.
*/
td->td_stopsched = 1;
#endif
bootopt = RB_AUTOBOOT;
@ -632,8 +614,6 @@ panic(const char *fmt, ...)
/* thread_unlock(td); */
if (!sync_on_panic)
bootopt |= RB_NOSYNC;
if (!stop_scheduler_on_panic)
critical_exit();
kern_reboot(bootopt);
}