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Do some refactoring and minor cleanups of the thread_single() code in

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preparation for the global stop commit.

Move the code to weed suspended or sleeping threads into the
appropriate state, into the helper weed_inhib().  Current code already
has deep nesting and hard to follow [1].

Add currently useless helper remain_for_mode(), which returns the
count of threads which are allowed to run, according to the
single-threading mode.

In thread_single_end(), do not save curthread into local variable, it
is unused after, except to find curproc.

Remove stray empty line.

Requested by:	avg [1]
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2014-12-08 16:27:43 +00:00
parent 8638fe7bea
commit 07a9368a48
1 changed files with 47 additions and 41 deletions
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88
sys/kern/kern_thread.c
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@ -64,7 +64,6 @@ __FBSDID("$FreeBSD$");
SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE(proc, , , lwp__exit);
/*
* thread related storage.
*/
@ -584,6 +583,46 @@ calc_remaining(struct proc *p, int mode)
return (remaining);
}
static int
remain_for_mode(int mode)
{
return (1);
}
static int
weed_inhib(int mode, struct thread *td2, struct proc *p)
{
int wakeup_swapper;
PROC_LOCK_ASSERT(p, MA_OWNED);
PROC_SLOCK_ASSERT(p, MA_OWNED);
THREAD_LOCK_ASSERT(td2, MA_OWNED);
wakeup_swapper = 0;
switch (mode) {
case SINGLE_EXIT:
if (TD_IS_SUSPENDED(td2))
wakeup_swapper |= thread_unsuspend_one(td2);
if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
wakeup_swapper |= sleepq_abort(td2, EINTR);
break;
case SINGLE_BOUNDARY:
if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0)
wakeup_swapper |= thread_unsuspend_one(td2);
if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
wakeup_swapper |= sleepq_abort(td2, ERESTART);
break;
case SINGLE_NO_EXIT:
if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0)
wakeup_swapper |= thread_unsuspend_one(td2);
if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
wakeup_swapper |= sleepq_abort(td2, ERESTART);
break;
}
return (wakeup_swapper);
}
/*
* Enforce single-threading.
*
@ -631,7 +670,7 @@ thread_single(int mode)
PROC_SLOCK(p);
p->p_singlethread = td;
remaining = calc_remaining(p, mode);
while (remaining != 1) {
while (remaining != remain_for_mode(mode)) {
if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
goto stopme;
wakeup_swapper = 0;
@ -640,41 +679,8 @@ thread_single(int mode)
continue;
thread_lock(td2);
td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
if (TD_IS_INHIBITED(td2)) {
switch (mode) {
case SINGLE_EXIT:
if (TD_IS_SUSPENDED(td2))
wakeup_swapper |=
thread_unsuspend_one(td2);
if (TD_ON_SLEEPQ(td2) &&
(td2->td_flags & TDF_SINTR))
wakeup_swapper |=
sleepq_abort(td2, EINTR);
break;
case SINGLE_BOUNDARY:
if (TD_IS_SUSPENDED(td2) &&
!(td2->td_flags & TDF_BOUNDARY))
wakeup_swapper |=
thread_unsuspend_one(td2);
if (TD_ON_SLEEPQ(td2) &&
(td2->td_flags & TDF_SINTR))
wakeup_swapper |=
sleepq_abort(td2, ERESTART);
break;
case SINGLE_NO_EXIT:
if (TD_IS_SUSPENDED(td2) &&
!(td2->td_flags & TDF_BOUNDARY))
wakeup_swapper |=
thread_unsuspend_one(td2);
if (TD_ON_SLEEPQ(td2) &&
(td2->td_flags & TDF_SINTR))
wakeup_swapper |=
sleepq_abort(td2, ERESTART);
break;
default:
break;
}
}
if (TD_IS_INHIBITED(td2))
wakeup_swapper |= weed_inhib(mode, td2, p);
#ifdef SMP
else if (TD_IS_RUNNING(td2) && td != td2) {
forward_signal(td2);
@ -689,7 +695,7 @@ thread_single(int mode)
/*
* Maybe we suspended some threads.. was it enough?
*/
if (remaining == 1)
if (remaining == remain_for_mode(mode))
break;
stopme:
@ -968,8 +974,7 @@ thread_single_end(void)
struct proc *p;
int wakeup_swapper;
td = curthread;
p = td->td_proc;
p = curproc;
PROC_LOCK_ASSERT(p, MA_OWNED);
p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
PROC_SLOCK(p);
@ -981,7 +986,8 @@ thread_single_end(void)
* on the process. The single threader must be allowed
* to continue however as this is a bad place to stop.
*/
if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
if (p->p_numthreads != remain_for_mode(SINGLE_EXIT) &&
!P_SHOULDSTOP(p)) {
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (TD_IS_SUSPENDED(td)) {