diff options
| author | Mateusz Guzik <mjg@FreeBSD.org> | 2025-09-25 11:50:01 +0000 |
|---|---|---|
| committer | Mateusz Guzik <mjg@FreeBSD.org> | 2025-09-25 11:50:55 +0000 |
| commit | a15f2c5cc58f403407daf797a2e6963adffa6c2c (patch) | |
| tree | ddaeadf5cc9ed88b9e5388b5e8d3b48f6d3a859d | |
| parent | b0091036f7240ab244e86a087b18459185a260de (diff) | |
proc: perform P_CONTROLT check on fork without SESS_LOCK
The flag is guarded by proc lock which is already held.
After tracing poudriere for over 4 hours like so:
dtrace -n 'fbt::do_fork:entry { @[curthread->td_proc->p_flag & 0x2] = count(); }':
2 15605151
0 20074116
Over 56% of cases did not have P_CONTROLT set and could have avoided the
lock.
This reduces hold time of the proctree lock.
| -rw-r--r-- | sys/kern/kern_fork.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c index 2ab9b363f8b5..7f6abae187b3 100644 --- a/sys/kern/kern_fork.c +++ b/sys/kern/kern_fork.c @@ -610,10 +610,12 @@ do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread * p2->p_flag |= p1->p_flag & P_SUGID; td2->td_pflags |= td->td_pflags & (TDP_ALTSTACK | TDP_SIGFASTBLOCK); td2->td_pflags2 |= td->td_pflags2 & TDP2_UEXTERR; - SESS_LOCK(p1->p_session); - if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) - p2->p_flag |= P_CONTROLT; - SESS_UNLOCK(p1->p_session); + if (p1->p_flag & P_CONTROLT) { + SESS_LOCK(p1->p_session); + if (p1->p_session->s_ttyvp != NULL) + p2->p_flag |= P_CONTROLT; + SESS_UNLOCK(p1->p_session); + } if (fr->fr_flags & RFPPWAIT) p2->p_flag |= P_PPWAIT; |