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exec: get rid of one vnode lock/unlock pair in do_execve

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The lock was temporarily dropped for vrele calls, but they can be
postponed to a point where the lock is not held in the first place.

While here shuffle other code not needing the lock.
This commit is contained in:
Mateusz Guzik 2016-05-27 15:03:38 +00:00
parent 12aac6b55b
commit cda688443a
1 changed files with 31 additions and 43 deletions
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74
sys/kern/kern_exec.c
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@ -364,7 +364,7 @@ do_execve(td, args, mac_p)
struct vattr attr;
int (*img_first)(struct image_params *);
struct pargs *oldargs = NULL, *newargs = NULL;
struct sigacts *oldsigacts, *newsigacts;
struct sigacts *oldsigacts = NULL, *newsigacts = NULL;
#ifdef KTRACE
struct vnode *tracevp = NULL;
struct ucred *tracecred = NULL;
@ -714,8 +714,6 @@ do_execve(td, args, mac_p)
bcopy(imgp->args->begin_argv, newargs->ar_args, i);
}
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
/*
* For security and other reasons, signal handlers cannot
* be shared after an exec. The new process gets a copy of the old
@ -726,11 +724,10 @@ do_execve(td, args, mac_p)
oldsigacts = p->p_sigacts;
newsigacts = sigacts_alloc();
sigacts_copy(newsigacts, oldsigacts);
} else {
oldsigacts = NULL;
newsigacts = NULL; /* satisfy gcc */
}
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
PROC_LOCK(p);
if (oldsigacts)
p->p_sigacts = newsigacts;
@ -791,9 +788,9 @@ do_execve(td, args, mac_p)
VOP_UNLOCK(imgp->vp, 0);
fdsetugidsafety(td);
error = fdcheckstd(td);
if (error != 0)
goto done1;
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
if (error != 0)
goto exec_fail_dealloc;
PROC_LOCK(p);
#ifdef MAC
if (will_transition) {
@ -881,32 +878,7 @@ do_execve(td, args, mac_p)
SDT_PROBE1(proc, , , exec__success, args->fname);
VOP_UNLOCK(imgp->vp, 0);
done1:
/*
* Handle deferred decrement of ref counts.
*/
if (oldtextvp != NULL)
vrele(oldtextvp);
#ifdef KTRACE
if (tracevp != NULL)
vrele(tracevp);
if (tracecred != NULL)
crfree(tracecred);
#endif
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
pargs_drop(oldargs);
pargs_drop(newargs);
if (oldsigacts != NULL)
sigacts_free(oldsigacts);
exec_fail_dealloc:
/*
* free various allocated resources
*/
if (euip != NULL)
uifree(euip);
if (imgp->firstpage != NULL)
exec_unmap_first_page(imgp);
@ -936,18 +908,16 @@ do_execve(td, args, mac_p)
* the S_EXEC bit set.
*/
STOPEVENT(p, S_EXEC, 0);
goto done2;
} else {
exec_fail:
/* we're done here, clear P_INEXEC */
PROC_LOCK(p);
p->p_flag &= ~P_INEXEC;
PROC_UNLOCK(p);
SDT_PROBE1(proc, , , exec__failure, error);
}
exec_fail:
/* we're done here, clear P_INEXEC */
PROC_LOCK(p);
p->p_flag &= ~P_INEXEC;
PROC_UNLOCK(p);
SDT_PROBE1(proc, , , exec__failure, error);
done2:
if (imgp->newcred != NULL)
crfree(oldcred);
#ifdef MAC
@ -956,6 +926,24 @@ do_execve(td, args, mac_p)
#endif
exec_free_args(args);
/*
* Handle deferred decrement of ref counts.
*/
if (oldtextvp != NULL)
vrele(oldtextvp);
#ifdef KTRACE
if (tracevp != NULL)
vrele(tracevp);
if (tracecred != NULL)
crfree(tracecred);
#endif
pargs_drop(oldargs);
pargs_drop(newargs);
if (oldsigacts != NULL)
sigacts_free(oldsigacts);
if (euip != NULL)
uifree(euip);
if (error && imgp->vmspace_destroyed) {
/* sorry, no more process anymore. exit gracefully */
exit1(td, 0, SIGABRT);