The branch main has been updated by melifaro:
URL:
https://cgit.FreeBSD.org/src/commit/?id=5bdce6ff546e00673f9f515d2165d02901e858aa
commit 5bdce6ff546e00673f9f515d2165d02901e858aa
Author: Alexander V. Chernikov <melif...@freebsd.org>
AuthorDate: 2021-01-21 21:26:15 +0000
Commit: Alexander V. Chernikov <melif...@freebsd.org>
CommitDate: 2021-01-21 21:36:37 +0000
Remove deadlock in rc caused by pwait waiting for itself.
The following situation can trigger the deadlock:
1) Long time ago a_service was started through rc.d
2) We want to restart a_service and issue service a_service restart
3) rc.subr reads current process PID (via file or process),
sends TERM signal and runs pwait with PID harvested
4) a_service process dies very quickly so it's PID becomes available.
It is possible that while original process was running,
PID counter overflowed and pwait got assigned a_service's PID.
This patch ignores pid(s) to wait that are equal to pwait PID.
Reported by: Dan McGregor, Boris Lytochkin
Submitted by: Boris Lytochkin <lytboris at gmail.com>
Reviewed By: 0mp
MFC after: 2 weeks
PR: 218598
Differential Revision: https://reviews.freebsd.org/D28240
---
bin/pwait/pwait.1 | 6 +++++-
bin/pwait/pwait.c | 4 ++++
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/bin/pwait/pwait.1 b/bin/pwait/pwait.1
index 0452203eb4a1..b9b651bfc905 100644
--- a/bin/pwait/pwait.1
+++ b/bin/pwait/pwait.1
@@ -32,7 +32,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd October 5, 2020
+.Dd January 21, 2021
.Dt PWAIT 1
.Os
.Sh NAME
@@ -145,6 +145,10 @@ is not a substitute for the
.Xr wait 1
builtin
as it will not clean up any zombies or state in the parent process.
+.Pp
+To avoid deadlock,
+.Nm
+will ignore its own pid, if it is provided as a process id to wait for.
.Sh HISTORY
A
.Nm
diff --git a/bin/pwait/pwait.c b/bin/pwait/pwait.c
index f39922b48eb9..85cc6b994acf 100644
--- a/bin/pwait/pwait.c
+++ b/bin/pwait/pwait.c
@@ -146,6 +146,10 @@ main(int argc, char *argv[])
warnx("%s: bad process id", s);
continue;
}
+ if (pid == getpid()) {
+ warnx("%s: skiping my own pid", s);
+ continue;
+ }
for (i = 0; i < nleft; i++) {
if (e[i].ident == (uintptr_t)pid) {
break;
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