Deinline vfork handling out of the syscall return path.

vfork is rarely called (comparatively to other syscalls) and it avoidably
pollutes the fast path.

Sponsored by:	The FreeBSD Foundation

1 files changed, 45 insertions, 0 deletions

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index acba58b89c8f..f897f78b48ca 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -757,6 +757,51 @@ do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *
 	}
 }
 
+void
+fork_rfppwait(struct thread *td)
+{
+	struct proc *p, *p2;
+
+	MPASS(td->td_pflags & TDP_RFPPWAIT);
+
+	p = td->td_proc;
+	/*
+	 * Preserve synchronization semantics of vfork.  If
+	 * waiting for child to exec or exit, fork set
+	 * P_PPWAIT on child, and there we sleep on our proc
+	 * (in case of exit).
+	 *
+	 * Do it after the ptracestop() above is finished, to
+	 * not block our debugger until child execs or exits
+	 * to finish vfork wait.
+	 */
+	td->td_pflags &= ~TDP_RFPPWAIT;
+	p2 = td->td_rfppwait_p;
+again:
+	PROC_LOCK(p2);
+	while (p2->p_flag & P_PPWAIT) {
+		PROC_LOCK(p);
+		if (thread_suspend_check_needed()) {
+			PROC_UNLOCK(p2);
+			thread_suspend_check(0);
+			PROC_UNLOCK(p);
+			goto again;
+		} else {
+			PROC_UNLOCK(p);
+		}
+		cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz);
+	}
+	PROC_UNLOCK(p2);
+
+	if (td->td_dbgflags & TDB_VFORK) {
+		PROC_LOCK(p);
+		if (p->p_ptevents & PTRACE_VFORK)
+			ptracestop(td, SIGTRAP, NULL);
+		td->td_dbgflags &= ~TDB_VFORK;
+		PROC_UNLOCK(p);
+	}
+}
+
 int
 fork1(struct thread *td, struct fork_req *fr)
 {