Fix some locking nits with the p_state field of struct proc:
- Hold the proc lock while changing the state from PRS_NEW to PRS_NORMAL in fork to honor the locking requirements. While here, expand the scope of the PROC_LOCK() on the new process (p2) to avoid some LORs. Previously the code was locking the new child process (p2) after it had locked the parent process (p1). However, when locking two processes, the safe order is to lock the child first, then the parent. - Fix various places that were checking p_state against PRS_NEW without having the process locked to use PROC_LOCK(). Every place was already locking the process, just after the PRS_NEW check. - Remove or reduce the use of PROC_SLOCK() for places that were checking p_state against PRS_NEW. The PROC_LOCK() alone is sufficient for reading the current state. - Reorder fill_kinfo_proc() slightly so it only acquires PROC_SLOCK() once. MFC after: 1 week
This commit is contained in:
parent
3bf92decd3
commit
8e6fa660f2
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=219968
@ -740,7 +740,6 @@ linprocfs_doprocstatus(PFS_FILL_ARGS)
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if (P_SHOULDSTOP(p)) {
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state = "T (stopped)";
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} else {
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PROC_SLOCK(p);
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switch(p->p_state) {
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case PRS_NEW:
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state = "I (idle)";
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@ -770,7 +769,6 @@ linprocfs_doprocstatus(PFS_FILL_ARGS)
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state = "? (unknown)";
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break;
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}
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PROC_SUNLOCK(p);
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}
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fill_kinfo_proc(p, &kp);
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@ -1102,11 +1102,11 @@ pfind_locked(pid_t pid)
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LIST_FOREACH(p, PIDHASH(pid), p_hash)
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if (p->p_pid == pid) {
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if (p->p_state == PRS_NEW) {
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p = NULL;
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break;
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}
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PROC_LOCK(p);
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if (p->p_state == PRS_NEW) {
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PROC_UNLOCK(p);
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p = NULL;
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}
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break;
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}
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return (p);
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@ -2634,9 +2634,11 @@ sysctl_kern_file(SYSCTL_HANDLER_ARGS)
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xf.xf_size = sizeof(xf);
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sx_slock(&allproc_lock);
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FOREACH_PROC_IN_SYSTEM(p) {
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if (p->p_state == PRS_NEW)
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continue;
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PROC_LOCK(p);
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if (p->p_state == PRS_NEW) {
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PROC_UNLOCK(p);
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continue;
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}
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if (p_cansee(req->td, p) != 0) {
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PROC_UNLOCK(p);
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continue;
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@ -630,12 +630,13 @@ do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
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/*
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* Set the child start time and mark the process as being complete.
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*/
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PROC_LOCK(p2);
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PROC_LOCK(p1);
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microuptime(&p2->p_stats->p_start);
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PROC_SLOCK(p2);
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p2->p_state = PRS_NORMAL;
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PROC_SUNLOCK(p2);
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PROC_LOCK(p1);
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#ifdef KDTRACE_HOOKS
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/*
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* Tell the DTrace fasttrap provider about the new process
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@ -643,11 +644,8 @@ do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
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* p_state is PRS_NORMAL since the fasttrap module will use pfind()
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* later on.
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*/
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if (dtrace_fasttrap_fork) {
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PROC_LOCK(p2);
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if (dtrace_fasttrap_fork)
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dtrace_fasttrap_fork(p1, p2);
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PROC_UNLOCK(p2);
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}
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#endif
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if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
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P_FOLLOWFORK)) {
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@ -660,12 +658,11 @@ do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
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*/
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td->td_dbgflags |= TDB_FORK;
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td->td_dbg_forked = p2->p_pid;
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PROC_LOCK(p2);
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td2->td_dbgflags |= TDB_STOPATFORK;
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_PHOLD(p2);
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p2_held = 1;
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PROC_UNLOCK(p2);
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}
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PROC_UNLOCK(p2);
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if ((flags & RFSTOPPED) == 0) {
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/*
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* If RFSTOPPED not requested, make child runnable and
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@ -291,11 +291,11 @@ pfind(pid)
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sx_slock(&allproc_lock);
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LIST_FOREACH(p, PIDHASH(pid), p_hash)
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if (p->p_pid == pid) {
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if (p->p_state == PRS_NEW) {
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p = NULL;
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break;
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}
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PROC_LOCK(p);
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if (p->p_state == PRS_NEW) {
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PROC_UNLOCK(p);
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p = NULL;
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}
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break;
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}
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sx_sunlock(&allproc_lock);
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@ -756,7 +756,6 @@ fill_kinfo_proc_only(struct proc *p, struct kinfo_proc *kp)
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kp->ki_sigcatch = ps->ps_sigcatch;
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mtx_unlock(&ps->ps_mtx);
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}
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PROC_SLOCK(p);
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if (p->p_state != PRS_NEW &&
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p->p_state != PRS_ZOMBIE &&
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p->p_vmspace != NULL) {
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@ -782,12 +781,11 @@ fill_kinfo_proc_only(struct proc *p, struct kinfo_proc *kp)
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kp->ki_swtime = (ticks - p->p_swtick) / hz;
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kp->ki_pid = p->p_pid;
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kp->ki_nice = p->p_nice;
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rufetch(p, &kp->ki_rusage);
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kp->ki_runtime = cputick2usec(p->p_rux.rux_runtime);
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PROC_SUNLOCK(p);
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kp->ki_start = p->p_stats->p_start;
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timevaladd(&kp->ki_start, &boottime);
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PROC_SLOCK(p);
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rufetch(p, &kp->ki_rusage);
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kp->ki_runtime = cputick2usec(p->p_rux.rux_runtime);
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calcru(p, &kp->ki_rusage.ru_utime, &kp->ki_rusage.ru_stime);
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PROC_SUNLOCK(p);
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calccru(p, &kp->ki_childutime, &kp->ki_childstime);
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@ -1213,13 +1211,11 @@ sysctl_kern_proc(SYSCTL_HANDLER_ARGS)
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/*
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* Skip embryonic processes.
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*/
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PROC_SLOCK(p);
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PROC_LOCK(p);
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if (p->p_state == PRS_NEW) {
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PROC_SUNLOCK(p);
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PROC_UNLOCK(p);
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continue;
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}
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PROC_SUNLOCK(p);
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PROC_LOCK(p);
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KASSERT(p->p_ucred != NULL,
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("process credential is NULL for non-NEW proc"));
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/*
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@ -142,11 +142,9 @@ getpriority(td, uap)
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uap->who = td->td_ucred->cr_uid;
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sx_slock(&allproc_lock);
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FOREACH_PROC_IN_SYSTEM(p) {
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/* Do not bother to check PRS_NEW processes */
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if (p->p_state == PRS_NEW)
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continue;
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PROC_LOCK(p);
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if (p_cansee(td, p) == 0 &&
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if (p->p_state == PRS_NORMAL &&
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p_cansee(td, p) == 0 &&
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p->p_ucred->cr_uid == uap->who) {
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if (p->p_nice < low)
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low = p->p_nice;
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@ -981,7 +981,9 @@ tdfind(lwpid_t tid, pid_t pid)
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td = NULL;
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break;
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}
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PROC_LOCK(td->td_proc);
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if (td->td_proc->p_state == PRS_NEW) {
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PROC_UNLOCK(td->td_proc);
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td = NULL;
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break;
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}
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@ -990,12 +992,10 @@ tdfind(lwpid_t tid, pid_t pid)
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LIST_REMOVE(td, td_hash);
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LIST_INSERT_HEAD(TIDHASH(td->td_tid),
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td, td_hash);
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PROC_LOCK(td->td_proc);
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rw_wunlock(&tidhash_lock);
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return (td);
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}
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}
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PROC_LOCK(td->td_proc);
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break;
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}
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run++;
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@ -130,15 +130,12 @@ vmtotal(SYSCTL_HANDLER_ARGS)
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if (p->p_flag & P_SYSTEM)
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continue;
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PROC_LOCK(p);
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PROC_SLOCK(p);
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switch (p->p_state) {
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case PRS_NEW:
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PROC_SUNLOCK(p);
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PROC_UNLOCK(p);
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continue;
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break;
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default:
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PROC_SUNLOCK(p);
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FOREACH_THREAD_IN_PROC(p, td) {
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thread_lock(td);
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switch (td->td_state) {
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@ -1281,14 +1281,13 @@ vm_pageout_oom(int shortage)
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FOREACH_PROC_IN_SYSTEM(p) {
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int breakout;
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if (p->p_state != PRS_NORMAL)
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continue;
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if (PROC_TRYLOCK(p) == 0)
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continue;
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/*
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* If this is a system, protected or killed process, skip it.
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*/
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if ((p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) ||
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if (p->p_state != PRS_NORMAL ||
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(p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) ||
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(p->p_pid == 1) || P_KILLED(p) ||
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((p->p_pid < 48) && (swap_pager_avail != 0))) {
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PROC_UNLOCK(p);
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@ -1651,14 +1650,13 @@ vm_daemon()
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FOREACH_PROC_IN_SYSTEM(p) {
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vm_pindex_t limit, size;
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if (p->p_state != PRS_NORMAL)
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continue;
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/*
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* if this is a system process or if we have already
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* looked at this process, skip it.
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*/
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PROC_LOCK(p);
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if (p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
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if (p->p_state != PRS_NORMAL ||
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p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
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PROC_UNLOCK(p);
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continue;
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}
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