ash: jobs: Block signals during tcsetpgrp

Merge upstream commit 4ce8afe6b.  This has no effect on Windows.

1 files changed, 16 insertions, 1 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 09e9ef605..408027305 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -4712,7 +4712,22 @@ freejob(struct job *jp)
 static void
 xtcsetpgrp(int fd, pid_t pgrp)
 {
-        if (tcsetpgrp(fd, pgrp))
+        int err;
+
+        sigblockall(NULL);
+        err = tcsetpgrp(fd, pgrp);
+        sigclearmask();
+        // Unmasking signals would cause any arrived signal to trigger, so why?
+        // Generally yes, but there are exceptions. Such as:
+        // """
+        // Attempts to use tcsetpgrp() from a process which is a member of
+        // a background process group on a fd associated with its controlling
+        // terminal shall cause the process group to be sent a SIGTTOU signal.
+        // If the calling thread is blocking SIGTTOU signals or the process
+        // is ignoring SIGTTOU signals, the process shall be allowed
+        // to perform the operation, and no signal is sent."""
+
+        if (err)
                 ash_msg_and_raise_perror("can't set tty process group");
 }