Don't leak a signalfd when using latches in the postmaster.

At the time of commit 6a2a70a02 we didn't use latch infrastructure in
the postmaster.  We're planning to start doing that, so we'd better make
sure that the signalfd inherited from a postmaster is not duplicated and
then leaked in the child.

Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/CA%2BhUKG%2BZ-HpOj1JsO9eWUP%2Bar7npSVinsC_npxSy%2BjdOMsx%3DGg%40mail.gmail.com

diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c
index 7ced8264f00b82ff642196063c7ce5807d556acb..b32c96b63d3b41eee1d73df9d7e2764f429207f7 100644 (file)
--- a/src/backend/storage/ipc/latch.c
+++ b/src/backend/storage/ipc/latch.c
@@ -283,6 +283,22 @@ InitializeLatchSupport(void)
 #ifdef WAIT_USE_SIGNALFD
    sigset_t    signalfd_mask;
 
+   if (IsUnderPostmaster)
+   {
+       /*
+        * It would probably be safe to re-use the inherited signalfd since
+        * signalfds only see the current process's pending signals, but it
+        * seems less surprising to close it and create our own.
+        */
+       if (signal_fd != -1)
+       {
+           /* Release postmaster's signal FD; ignore any error */
+           (void) close(signal_fd);
+           signal_fd = -1;
+           ReleaseExternalFD();
+       }
+   }
+
    /* Block SIGURG, because we'll receive it through a signalfd. */
    sigaddset(&UnBlockSig, SIGURG);