From ed2589219056458a20aa399d128e06394f632e15 Mon Sep 17 00:00:00 2001
From: mar77i <mar77i@users.noreply.github.com>
Date: Fri, 11 Apr 2014 11:15:04 +0200
Subject: lock.c: Truls Beckens was right #2

also, what the hell?

Fixed the obvious stuff and returned atomicity to the locking - no, access() isn't safe when you want that.
---
 lock.c | 39 ++++++++++-----------------------------
 1 file changed, 10 insertions(+), 29 deletions(-)

(limited to 'lock.c')

diff --git a/lock.c b/lock.c
index 68245ac..aaac35a 100644
--- a/lock.c
+++ b/lock.c
@@ -1,4 +1,5 @@
 /* See LICENSE for licence details. */
+#include <errno.h>
 #include <string.h>
 #include <stdio.h>
 #include <unistd.h>
@@ -14,39 +15,19 @@ int main(int argc, char **argv){
 		return EXIT_FAILURE;
 	}
 
-	if(access(argv[1], F_OK)){
-		/* create lock */
-		if(mkdir(argv[1], S_IRUSR | S_IXUSR)){
+	/* create lock */
+	if(mkdir(argv[1], S_IRUSR | S_IXUSR)){
+		if(errno && errno != EEXIST) {
 			fprintf(stderr, "Failed to create lock %s.\n", argv[1]);
 			return EXIT_FAILURE;
 		}
+		/* lock exists */
+		for(; mkdir(argv[1], S_IRUSR | S_IXUSR);){
+			sleep(1);
+		}
+		return EXIT_SUCCESS;
+	} else
 		return EXIT_SUCCESS;
 	}
 	
-	/* prepare path */
-	argvlen = strlen(argv[1]);
-	pathlen = argvlen + sizeof("/..") + 1;
-	path = malloc(pathlen);
-	if(path == NULL) {
-		fprintf(stderr, "malloc() failed\n");
-		return EXIT_FAILURE;
-	}
-	
-	memcpy(path, argv[1], argvlen);
-	memcpy(path + argvlen, "/..\0", sizeof("/..") + 1);
-
-	if(access(path, F_OK)){
-		/* invalid lock */
-		fprintf(stderr, "%s is not a lock directory.\n", argv[1]);
-		free(path);
-		return EXIT_FAILURE;
-	}
-	
-	/* lock exists */
-	for(; !access(path, F_OK) ;){
-		sleep(1);
-	}
-
-	free(path);
-	return EXIT_SUCCESS;
 }
-- 
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