Make SIGSTOP working for sleeps done while waiting for fifo readers or

writers in open(2), when the fifo is located on an NFS mount.

Reported by:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

3 files changed, 13 insertions, 4 deletions

diff --git a/sys/fs/fifofs/fifo_vnops.c b/sys/fs/fifofs/fifo_vnops.c
index a3e8179..e544bba 100644
--- a/sys/fs/fifofs/fifo_vnops.c
+++ b/sys/fs/fifofs/fifo_vnops.c
@@ -137,7 +137,7 @@ fifo_open(ap)
 	struct thread *td;
 	struct fifoinfo *fip;
 	struct pipe *fpipe;
-	int error;
+	int error, stops_deferred;
 
 	vp = ap->a_vp;
 	fp = ap->a_fp;
@@ -188,8 +188,11 @@ fifo_open(ap)
 	if ((ap->a_mode & O_NONBLOCK) == 0) {
 		if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
 			VOP_UNLOCK(vp, 0);
+			stops_deferred = sigallowstop();
 			error = msleep(&fip->fi_readers, PIPE_MTX(fpipe),
 			    PDROP | PCATCH | PSOCK, "fifoor", 0);
+			if (stops_deferred)
+				sigdeferstop();
 			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 			if (error) {
 				fip->fi_readers--;
@@ -212,8 +215,11 @@ fifo_open(ap)
 		}
 		if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
 			VOP_UNLOCK(vp, 0);
+			stops_deferred = sigallowstop();
 			error = msleep(&fip->fi_writers, PIPE_MTX(fpipe),
 			    PDROP | PCATCH | PSOCK, "fifoow", 0);
+			if (stops_deferred)
+				sigdeferstop();
 			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 			if (error) {
 				fip->fi_writers--;
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 06d8e99..e60e09d 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -2587,15 +2587,18 @@ sigdeferstop(void)
  * not immediately suspend if a stop was posted.  Instead, the thread
  * will suspend either via ast() or a subsequent interruptible sleep.
  */
-void
-sigallowstop()
+int
+sigallowstop(void)
 {
 	struct thread *td;
+	int prev;
 
 	td = curthread;
 	thread_lock(td);
+	prev = (td->td_flags & TDF_SBDRY) != 0;
 	td->td_flags &= ~TDF_SBDRY;
 	thread_unlock(td);
+	return (prev);
 }
 
 /*
diff --git a/sys/sys/signalvar.h b/sys/sys/signalvar.h
index f7fcaa9..f033702 100644
--- a/sys/sys/signalvar.h
+++ b/sys/sys/signalvar.h
@@ -325,7 +325,7 @@ extern struct mtx	sigio_lock;
 
 int	cursig(struct thread *td);
 int	sigdeferstop(void);
-void	sigallowstop(void);
+int	sigallowstop(void);
 void	execsigs(struct proc *p);
 void	gsignal(int pgid, int sig, ksiginfo_t *ksi);
 void	killproc(struct proc *p, char *why);