X-Git-Url: http://pileus.org/git/?a=blobdiff_plain;f=lock.c;h=213969f1f012f323c470ceb3a1e6b1c1aec43ffa;hb=5b0e1fdef9c55b9c8a54f5c146fc84dab3b82e63;hp=39351be1f4bac84f98800539f841be48d18fdcb2;hpb=08f6a9bfc9a9ef93767f9fdcbc5c1991a943061a;p=~andy%2Ffetchmail

diff --git a/lock.c b/lock.c
index 39351be1..213969f1 100644
--- a/lock.c
+++ b/lock.c
@@ -1,5 +1,5 @@
-/*
- * lock.c -- cross-platform concurrency locking for fetchmail
+/**
+ * \file lock.c cross-platform concurrency locking for fetchmail
  *
  * For license terms, see the file COPYING in this directory.
  */
@@ -23,8 +23,8 @@
 #include "i18n.h"
 #include "lock.h"
 
-static char *lockfile;		/* name of lockfile */
-static int lock_acquired;	/* have we acquired a lock */
+static char *lockfile;		/** name of lockfile */
+static int lock_acquired;	/** flag if have we acquired a lock */
 
 void fm_lock_setup(struct runctl *ctl)
 /* set up the global lockfile name */
@@ -73,32 +73,49 @@ void fm_lock_dispose(void)
 
 int fm_lock_state(void)
 {
-    int		pid, st;
+    long	pid;
+    int		st;
     FILE	*lockfp;
     int		bkgd = FALSE;
 
     if ((lockfp = fopen(lockfile, "r")) != NULL)
     {
-	int args = fscanf(lockfp, "%d %d", &pid, &st);
+	int args = fscanf(lockfp, "%ld %d", &pid, &st);
 	bkgd = (args == 2);
 
 	if (ferror(lockfp)) {
 	    fprintf(stderr, GT_("fetchmail: error reading lockfile \"%s\": %s\n"),
 		    lockfile, strerror(errno));
+	    fclose(lockfp); /* not checking should be safe, file mode was "r" */
 	    exit(PS_EXCLUDE);
 	}
+	fclose(lockfp); /* not checking should be safe, file mode was "r" */
 
-	if (args == 0 || kill(pid, 0) == -1) {
+	if (args == EOF || args == 0 || kill(pid, 0) == -1) {
+	    /* ^ could not read PID  || process does not exist */
+	    /* => lockfile is stale, unlink it */
 	    pid = 0;
+	    fprintf(stderr,GT_("fetchmail: removing stale lockfile\n"));
 	    if (unlink(lockfile)) {
 	       if (errno != ENOENT) {
 		   perror(lockfile);
+		   /* we complain but we don't exit; it might be
+		    * writable for us, but in a directory we cannot
+		    * write to. This means we can write the new PID to
+		    * the file. Truncate to be safe in case the PID is
+		    * recycled by another process later.
+		    * \bug we should use fcntl() style locks or
+		    * something else instead in a future release. */
+		   if (truncate(lockfile, (off_t)0)) {
+		       /* but if we cannot truncate the file either,
+			* assume that we cannot write to it later,
+			* complain and quit. */
+		       perror(lockfile);
+		       exit(PS_EXCLUDE);
+		   }
 	       }
-	    } else {
-		fprintf(stderr,GT_("fetchmail: removing stale lockfile\n"));
 	    }
 	}
-	fclose(lockfp); /* not checking should be safe, file mode was "r" */
     } else {
 	pid = 0;
 	if (errno != ENOENT) {
@@ -112,7 +129,7 @@ int fm_lock_state(void)
 }
 
 void fm_lock_assert(void)
-/* assert that we already posess a lock */
+/* assert that we already possess a lock */
 {
     lock_acquired = TRUE;
 }