From b2c846135dbc7cd0e5e226d9217f8716eb5f3a95 Mon Sep 17 00:00:00 2001
From: magnum <magnumripper@hushmail.com>
Date: Tue, 25 Feb 2025 15:10:33 +0100
Subject: [PATCH] Recover from (rare) non-fatal file locking problems

---
 src/locking.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/locking.c b/src/locking.c
index 8918101a2..492350bab 100644
--- a/src/locking.c
+++ b/src/locking.c
@@ -20,9 +20,18 @@ int hc_lockfile (HCFILE *fp)
 
   lock.l_type = F_WRLCK;
 
-  /* Needs this loop because a signal may interrupt a wait for lock */
   while (fcntl (fp->fd, F_SETLKW, &lock))
   {
+    // These shouldn't happen with F_SETLKW yet are (rarely) seen IRL. Recoverable!
+    if (errno == EAGAIN || errno == ENOLCK)
+    {
+      struct timeval tv = { .tv_sec = 0, .tv_usec = 10000 };
+      select (0, NULL, NULL, NULL, &tv);
+
+      continue;
+    }
+
+    // A signal may interrupt a wait for lock with EINTR. Anything else is fatal
     if (errno != EINTR) return -1;
   }