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Code Issues Releases Activity

Keep track of threads waiting in kse_release() to avoid a race

Browse Source 
condition where kse_wakeup() doesn't yet see them in (interruptible)
sleep queues.  Also add an upcall check to sleepqueue_catch_signals()
suggested by jhb.

This commit should fix recent mysql hangs.

Reviewed by:	jhb, davidxu
Mysql'd by:	Robin P. Blanchard <robin.blanchard at gactr uga edu>
This commit is contained in:
Daniel Eischen 2004-04-28 20:36:53 +00:00
parent d7837b06fe
commit 4fc21c0947
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=128721
4 changed files with 85 additions and 33 deletions
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53
sys/kern/kern_kse.c
View File

@ -621,9 +621,12 @@ kse_release(struct thread *td, struct kse_release_args *uap)
PROC_LOCK(p);
if (ku->ku_mflags & KMF_WAITSIGEVENT) {
/* UTS wants to wait for signal event */
if (!(p->p_flag & P_SIGEVENT) && !(ku->ku_flags & KUF_DOUPCALL))
if (!(p->p_flag & P_SIGEVENT) && !(ku->ku_flags & KUF_DOUPCALL)) {
td->td_kflags |= TDK_KSERELSIG;
error = msleep(&p->p_siglist, &p->p_mtx, PPAUSE|PCATCH,
"ksesigwait", (uap->timeout ? tvtohz(&tv) : 0));
td->td_kflags &= ~(TDK_KSERELSIG | TDK_WAKEUP);
}
p->p_flag &= ~P_SIGEVENT;
sigset = p->p_siglist;
PROC_UNLOCK(p);
@ -632,9 +635,11 @@ kse_release(struct thread *td, struct kse_release_args *uap)
} else {
if (! kg->kg_completed && !(ku->ku_flags & KUF_DOUPCALL)) {
kg->kg_upsleeps++;
td->td_kflags |= TDK_KSEREL;
error = msleep(&kg->kg_completed, &p->p_mtx,
PPAUSE|PCATCH, "kserel",
(uap->timeout ? tvtohz(&tv) : 0));
td->td_kflags &= ~(TDK_KSEREL | TDK_WAKEUP);
kg->kg_upsleeps--;
}
PROC_UNLOCK(p);
@ -678,31 +683,36 @@ kse_wakeup(struct thread *td, struct kse_wakeup_args *uap)
} else {
kg = td->td_ksegrp;
if (kg->kg_upsleeps) {
wakeup_one(&kg->kg_completed);
mtx_unlock_spin(&sched_lock);
wakeup_one(&kg->kg_completed);
PROC_UNLOCK(p);
return (0);
}
ku = TAILQ_FIRST(&kg->kg_upcalls);
}
if (ku) {
if ((td2 = ku->ku_owner) == NULL) {
panic("%s: no owner", __func__);
} else if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) &&
((td2->td_wchan == &kg->kg_completed) ||
(td2->td_wchan == &p->p_siglist &&
(ku->ku_mflags & KMF_WAITSIGEVENT)))) {
sleepq_abort(td2);
} else {
ku->ku_flags |= KUF_DOUPCALL;
}
if (ku == NULL) {
mtx_unlock_spin(&sched_lock);
PROC_UNLOCK(p);
return (0);
return (ESRCH);
}
if ((td2 = ku->ku_owner) == NULL) {
mtx_unlock_spin(&sched_lock);
panic("%s: no owner", __func__);
} else if (td2->td_kflags & (TDK_KSEREL | TDK_KSERELSIG)) {
mtx_unlock_spin(&sched_lock);
if (!(td2->td_kflags & TDK_WAKEUP)) {
td2->td_kflags |= TDK_WAKEUP;
if (td2->td_kflags & TDK_KSEREL)
sleepq_remove(td2, &kg->kg_completed);
else
sleepq_remove(td2, &p->p_siglist);
}
} else {
ku->ku_flags |= KUF_DOUPCALL;
mtx_unlock_spin(&sched_lock);
}
mtx_unlock_spin(&sched_lock);
PROC_UNLOCK(p);
return (ESRCH);
return (0);
}
/*
@ -1464,6 +1474,7 @@ thread_link(struct thread *td, struct ksegrp *kg)
td->td_ksegrp = kg;
td->td_last_kse = NULL;
td->td_flags = 0;
td->td_kflags = 0;
td->td_kse = NULL;
LIST_INIT(&td->td_contested);
@ -2222,3 +2233,13 @@ thread_single_end(void)
}
mtx_unlock_spin(&sched_lock);
}
int
thread_upcall_check(struct thread *td)
{
PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
if (td->td_kflags & TDK_WAKEUP)
return (1);
else
return (0);
}

53
sys/kern/kern_thread.c
View File

@ -621,9 +621,12 @@ kse_release(struct thread *td, struct kse_release_args *uap)
PROC_LOCK(p);
if (ku->ku_mflags & KMF_WAITSIGEVENT) {
/* UTS wants to wait for signal event */
if (!(p->p_flag & P_SIGEVENT) && !(ku->ku_flags & KUF_DOUPCALL))
if (!(p->p_flag & P_SIGEVENT) && !(ku->ku_flags & KUF_DOUPCALL)) {
td->td_kflags |= TDK_KSERELSIG;
error = msleep(&p->p_siglist, &p->p_mtx, PPAUSE|PCATCH,
"ksesigwait", (uap->timeout ? tvtohz(&tv) : 0));
td->td_kflags &= ~(TDK_KSERELSIG | TDK_WAKEUP);
}
p->p_flag &= ~P_SIGEVENT;
sigset = p->p_siglist;
PROC_UNLOCK(p);
@ -632,9 +635,11 @@ kse_release(struct thread *td, struct kse_release_args *uap)
} else {
if (! kg->kg_completed && !(ku->ku_flags & KUF_DOUPCALL)) {
kg->kg_upsleeps++;
td->td_kflags |= TDK_KSEREL;
error = msleep(&kg->kg_completed, &p->p_mtx,
PPAUSE|PCATCH, "kserel",
(uap->timeout ? tvtohz(&tv) : 0));
td->td_kflags &= ~(TDK_KSEREL | TDK_WAKEUP);
kg->kg_upsleeps--;
}
PROC_UNLOCK(p);
@ -678,31 +683,36 @@ kse_wakeup(struct thread *td, struct kse_wakeup_args *uap)
} else {
kg = td->td_ksegrp;
if (kg->kg_upsleeps) {
wakeup_one(&kg->kg_completed);
mtx_unlock_spin(&sched_lock);
wakeup_one(&kg->kg_completed);
PROC_UNLOCK(p);
return (0);
}
ku = TAILQ_FIRST(&kg->kg_upcalls);
}
if (ku) {
if ((td2 = ku->ku_owner) == NULL) {
panic("%s: no owner", __func__);
} else if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) &&
((td2->td_wchan == &kg->kg_completed) ||
(td2->td_wchan == &p->p_siglist &&
(ku->ku_mflags & KMF_WAITSIGEVENT)))) {
sleepq_abort(td2);
} else {
ku->ku_flags |= KUF_DOUPCALL;
}
if (ku == NULL) {
mtx_unlock_spin(&sched_lock);
PROC_UNLOCK(p);
return (0);
return (ESRCH);
}
if ((td2 = ku->ku_owner) == NULL) {
mtx_unlock_spin(&sched_lock);
panic("%s: no owner", __func__);
} else if (td2->td_kflags & (TDK_KSEREL | TDK_KSERELSIG)) {
mtx_unlock_spin(&sched_lock);
if (!(td2->td_kflags & TDK_WAKEUP)) {
td2->td_kflags |= TDK_WAKEUP;
if (td2->td_kflags & TDK_KSEREL)
sleepq_remove(td2, &kg->kg_completed);
else
sleepq_remove(td2, &p->p_siglist);
}
} else {
ku->ku_flags |= KUF_DOUPCALL;
mtx_unlock_spin(&sched_lock);
}
mtx_unlock_spin(&sched_lock);
PROC_UNLOCK(p);
return (ESRCH);
return (0);
}
/*
@ -1464,6 +1474,7 @@ thread_link(struct thread *td, struct ksegrp *kg)
td->td_ksegrp = kg;
td->td_last_kse = NULL;
td->td_flags = 0;
td->td_kflags = 0;
td->td_kse = NULL;
LIST_INIT(&td->td_contested);
@ -2222,3 +2233,13 @@ thread_single_end(void)
}
mtx_unlock_spin(&sched_lock);
}
int
thread_upcall_check(struct thread *td)
{
PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
if (td->td_kflags & TDK_WAKEUP)
return (1);
else
return (0);
}

6
sys/kern/subr_sleepqueue.c
View File

@ -293,8 +293,10 @@ sleepq_catch_signals(void *wchan)
struct sleepqueue *sq;
struct thread *td;
struct proc *p;
int do_upcall;
int sig;
do_upcall = 0;
td = curthread;
p = td->td_proc;
sc = SC_LOOKUP(wchan);
@ -318,6 +320,8 @@ sleepq_catch_signals(void *wchan)
mtx_unlock(&p->p_sigacts->ps_mtx);
if (sig == 0 && thread_suspend_check(1))
sig = SIGSTOP;
else
do_upcall = thread_upcall_check(td);
PROC_UNLOCK(p);
/*
@ -326,7 +330,7 @@ sleepq_catch_signals(void *wchan)
*/
sq = sleepq_lookup(wchan);
mtx_lock_spin(&sched_lock);
if (TD_ON_SLEEPQ(td) && sig != 0) {
if (TD_ON_SLEEPQ(td) && (sig != 0 || do_upcall != 0)) {
mtx_unlock_spin(&sched_lock);
sleepq_wakeup_thread(sq, td, -1);
} else

6
sys/sys/proc.h
View File

@ -302,6 +302,7 @@ struct thread {
TAILQ_ENTRY(thread) td_umtx; /* (c?) Link for when we're blocked. */
volatile u_int td_generation; /* (k) Enable detection of preemption */
stack_t td_sigstk; /* (k) Stack ptr and on-stack flag. */
int td_kflags; /* (c) Flags for KSE threading. */
#define td_endzero td_base_pri
@ -371,6 +372,10 @@ struct thread {
#define TDI_LOCK 0x0008 /* Stopped on a lock. */
#define TDI_IWAIT 0x0010 /* Awaiting interrupt. */
#define TDK_KSEREL 0x0001 /* Blocked in msleep on kg->kg_completed. */
#define TDK_KSERELSIG 0x0002 /* Blocked in msleep on p->p_siglist. */
#define TDK_WAKEUP 0x0004 /* Thread has been woken by kse_wakeup. */
#define TD_CAN_UNBIND(td) \
(((td)->td_flags & TDF_CAN_UNBIND) == TDF_CAN_UNBIND && \
((td)->td_upcall != NULL))
@ -913,6 +918,7 @@ void thread_unlink(struct thread *td);
void thread_unsuspend(struct proc *p);
void thread_unsuspend_one(struct thread *td);
int thread_userret(struct thread *td, struct trapframe *frame);
int thread_upcall_check(struct thread *td);
void thread_user_enter(struct proc *p, struct thread *td);
void thread_wait(struct proc *p);
int thread_statclock(int user);