locks: Protected racy (read) access of ext_list

Change-Id: Ibf639695ebd99c11c6960c9be82c0cee71b50744
BUG: 905864
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/4458
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 82 insertions, 0 deletions

diff --git a/tests/bugs/bug-905864.c b/tests/bugs/bug-905864.c
new file mode 100644
index 00000000000..ed09b6e2bc4
--- /dev/null
+++ b/tests/bugs/bug-905864.c
@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <pthread.h>
+
+
+pthread_t   th[5] = {0};
+void
+flock_init (struct flock *f, short int type, off_t start, off_t len)
+{
+    f->l_type = type;
+    f->l_start = start;
+    f->l_len = len;
+}
+
+int
+flock_range_in_steps (int fd, int is_set, short l_type,
+                      int start, int end, int step)
+{
+        int         ret = 0;
+        int         i = 0;
+        struct      flock f = {0,};
+
+        for (i = start; i+step < end; i += step) {
+                flock_init (&f, l_type, i, step);
+                ret = fcntl (fd, (is_set)? F_SETLKW:F_GETLK, &f);
+                if (ret) {
+                        perror ("fcntl");
+                        goto out;
+                }
+        }
+out:
+        return ret;
+}
+
+void *
+random_locker (void *arg)
+{
+        int         fd = *(int *)arg;
+        int         i = 0;
+        int         is_set = 0;
+
+        /* use thread id to choose GETLK or SETLK operation*/
+        is_set = pthread_self () % 2;
+        (void)flock_range_in_steps (fd, is_set, F_WRLCK, 0, 400, 1);
+
+        return NULL;
+}
+
+
+int main (int argc, char **argv)
+{
+        int         fd = -1;
+        int         ret = 1;
+        int         i = 0;
+        char        *fname = NULL;
+
+        if (argc < 2)
+                goto out;
+
+        fname = argv[1];
+        fd = open (fname, O_RDWR);
+        if (fd == -1) {
+                perror ("open");
+                goto out;
+        }
+
+        ret = flock_range_in_steps (fd, 1, F_WRLCK, 0, 2000, 2);
+        for (i = 0; i < 5; i++) {
+                pthread_create (&th[i], NULL, random_locker, (void *) &fd);
+        }
+        ret = flock_range_in_steps (fd, 1, F_WRLCK, 0, 2000, 2);
+        for (i = 0; i < 5; i++) {
+                pthread_join (th[i], NULL);
+        }
+out:
+        if (fd != -1)
+                close (fd);
+
+        return ret;
+}