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Perform a lockless check in sigacts_shared.

Browse source 
It is used only during execve (i.e. singlethreaded), so there is no fear
of returning 'not shared' which soon becomes 'shared'.

While here reorganize the code a little to avoid proc lock/unlock in
shared case.

MFC after:	1 week
This commit is contained in:
Mateusz Guzik 2014-07-01 06:29:15 +00:00
parent 601781ccc3
commit d00c8ea429
2 changed files with 5 additions and 10 deletions
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9
sys/kern/kern_exec.c
View file

@ -621,18 +621,17 @@ interpret:
* handlers. In execsigs(), the new process will have its signals
* reset.
*/
PROC_LOCK(p);
oldcred = crcopysafe(p, newcred);
if (sigacts_shared(p->p_sigacts)) {
oldsigacts = p->p_sigacts;
PROC_UNLOCK(p);
newsigacts = sigacts_alloc();
sigacts_copy(newsigacts, oldsigacts);
PROC_LOCK(p);
p->p_sigacts = newsigacts;
} else
oldsigacts = NULL;
PROC_LOCK(p);
if (oldsigacts)
p->p_sigacts = newsigacts;
oldcred = crcopysafe(p, newcred);
/* Stop profiling */
stopprofclock(p);

6
sys/kern/kern_sig.c
View file

@ -3453,10 +3453,6 @@ sigacts_copy(struct sigacts *dest, struct sigacts *src)
int
sigacts_shared(struct sigacts *ps)
{
int shared;
mtx_lock(&ps->ps_mtx);
shared = ps->ps_refcnt > 1;
mtx_unlock(&ps->ps_mtx);
return (shared);
return (ps->ps_refcnt > 1);
}