git: 02a2aacbe2c8 - main - issignal(): ignore signals when process is single-threading for exit

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=02a2aacbe2c81be455811fa9d4200101f70a86d2

commit 02a2aacbe2c81be455811fa9d4200101f70a86d2
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2022-05-26 19:18:57 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2022-06-13 19:30:02 +0000

    issignal(): ignore signals when process is single-threading for exit
    
    Places that will wait for curproc->p_singlethr to become zero (in the
    next commit, the counter of number of external single-threading is
    to be introduced), must wait for it interruptible, otherwise we
    deadlock.  On the other hand, a signal delivered during this window,
    if directed to the waiting thread, would cause the wait loop to become
    a busy loop.
    
    Since we are exiting, it is safe to ignore the signals.
    
    Reviewed by:    markj
    Tested by:      pho
    Sponsored by:   The FreeBSD Foundation
    MFC after:      2 weeks
    Differential revision:  https://reviews.freebsd.org/D35310
---
 sys/kern/kern_sig.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index afb2fd78c231..e3bbbd23ae6c 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -2928,7 +2928,7 @@ sigprocess(struct thread *td, int sig)
 
 	/*
 	 * We should allow pending but ignored signals below
-	 * only if there is sigwait() active, or P_TRACED was
+	 * if there is sigwait() active, or P_TRACED was
 	 * on when they were posted.
 	 */
 	if (SIGISMEMBER(ps->ps_sigignore, sig) &&
@@ -2937,6 +2937,16 @@ sigprocess(struct thread *td, int sig)
 		return (SIGSTATUS_IGNORE);
 	}
 
+	/*
+	 * If the process is going to single-thread mode to prepare
+	 * for exit, there is no sense in delivering any signal
+	 * to usermode.  Another important consequence is that
+	 * msleep(..., PCATCH, ...) now is only interruptible by a
+	 * suspend request.
+	 */
+	if ((p->p_flag2 & P2_WEXIT) != 0)
+		return (SIGSTATUS_IGNORE);
+
 	if ((p->p_flag & (P_TRACED | P_PPTRACE)) == P_TRACED) {
 		/*
 		 * If traced, always stop.