summaryrefslogtreecommitdiffstats
path: root/lib/tdb/test/run-fcntl-deadlock.c
diff options
context:
space:
mode:
Diffstat (limited to 'lib/tdb/test/run-fcntl-deadlock.c')
-rw-r--r--lib/tdb/test/run-fcntl-deadlock.c202
1 files changed, 202 insertions, 0 deletions
diff --git a/lib/tdb/test/run-fcntl-deadlock.c b/lib/tdb/test/run-fcntl-deadlock.c
new file mode 100644
index 0000000..0a328af
--- /dev/null
+++ b/lib/tdb/test/run-fcntl-deadlock.c
@@ -0,0 +1,202 @@
+#include "../common/tdb_private.h"
+#include "../common/io.c"
+#include "../common/tdb.c"
+#include "../common/lock.c"
+#include "../common/freelist.c"
+#include "../common/traverse.c"
+#include "../common/transaction.c"
+#include "../common/error.c"
+#include "../common/open.c"
+#include "../common/check.c"
+#include "../common/hash.c"
+#include "../common/mutex.c"
+#include "replace.h"
+#include "system/filesys.h"
+#include "system/time.h"
+#include <errno.h>
+#include "tap-interface.h"
+
+/*
+ * This tests the low level locking requirement
+ * for the allrecord lock/prepare_commit and traverse_read interaction.
+ *
+ * The pattern with the traverse_read and prepare_commit interaction is
+ * the following:
+ *
+ * 1. transaction_start got the allrecord lock with F_RDLCK.
+ *
+ * 2. the traverse_read code walks the database in a sequence like this
+ * (per chain):
+ * 2.1 chainlock(chainX, F_RDLCK)
+ * 2.2 recordlock(chainX.record1, F_RDLCK)
+ * 2.3 chainunlock(chainX, F_RDLCK)
+ * 2.4 callback(chainX.record1)
+ * 2.5 chainlock(chainX, F_RDLCK)
+ * 2.6 recordunlock(chainX.record1, F_RDLCK)
+ * 2.7 recordlock(chainX.record2, F_RDLCK)
+ * 2.8 chainunlock(chainX, F_RDLCK)
+ * 2.9 callback(chainX.record2)
+ * 2.10 chainlock(chainX, F_RDLCK)
+ * 2.11 recordunlock(chainX.record2, F_RDLCK)
+ * 2.12 chainunlock(chainX, F_RDLCK)
+ * 2.13 goto next chain
+ *
+ * So it has always one record locked in F_RDLCK mode and tries to
+ * get the 2nd one before it releases the first one.
+ *
+ * 3. prepare_commit tries to upgrade the allrecord lock to F_RWLCK
+ * If that happens at the time of 2.4, the operation of
+ * 2.5 may deadlock with the allrecord lock upgrade.
+ * On Linux step 2.5 works in order to make some progress with the
+ * locking, but on solaris it might fail because the kernel
+ * wants to satisfy the 1st lock requester before the 2nd one.
+ *
+ * I think the first step is a standalone test that does this:
+ *
+ * process1: F_RDLCK for ofs=0 len=2
+ * process2: F_RDLCK for ofs=0 len=1
+ * process1: upgrade ofs=0 len=2 to F_RWLCK (in blocking mode)
+ * process2: F_RDLCK for ofs=1 len=1
+ * process2: unlock ofs=0 len=2
+ * process1: should continue at that point
+ *
+ * Such a test follows here...
+ */
+
+static int raw_fcntl_lock(int fd, int rw, off_t off, off_t len, bool waitflag)
+{
+ struct flock fl;
+ int cmd;
+ fl.l_type = rw;
+ fl.l_whence = SEEK_SET;
+ fl.l_start = off;
+ fl.l_len = len;
+ fl.l_pid = 0;
+
+ cmd = waitflag ? F_SETLKW : F_SETLK;
+
+ return fcntl(fd, cmd, &fl);
+}
+
+static int raw_fcntl_unlock(int fd, off_t off, off_t len)
+{
+ struct flock fl;
+ fl.l_type = F_UNLCK;
+ fl.l_whence = SEEK_SET;
+ fl.l_start = off;
+ fl.l_len = len;
+ fl.l_pid = 0;
+
+ return fcntl(fd, F_SETLKW, &fl);
+}
+
+
+int pipe_r;
+int pipe_w;
+char buf[2];
+
+static void expect_char(char c)
+{
+ read(pipe_r, buf, 1);
+ if (*buf != c) {
+ fail("We were expecting %c, but got %c", c, buf[0]);
+ }
+}
+
+static void send_char(char c)
+{
+ write(pipe_w, &c, 1);
+}
+
+
+int main(int argc, char *argv[])
+{
+ int process;
+ int fd;
+ const char *filename = "run-fcntl-deadlock.lck";
+ int pid;
+ int pipes_1_2[2];
+ int pipes_2_1[2];
+ int ret;
+
+ pipe(pipes_1_2);
+ pipe(pipes_2_1);
+ fd = open(filename, O_RDWR | O_CREAT, 0755);
+
+ pid = fork();
+ if (pid == 0) {
+ pipe_r = pipes_1_2[0];
+ pipe_w = pipes_2_1[1];
+ process = 2;
+ alarm(15);
+ } else {
+ pipe_r = pipes_2_1[0];
+ pipe_w = pipes_1_2[1];
+ process = 1;
+ alarm(15);
+ }
+
+ /* a: process1: F_RDLCK for ofs=0 len=2 */
+ if (process == 1) {
+ ret = raw_fcntl_lock(fd, F_RDLCK, 0, 2, true);
+ ok(ret == 0,
+ "process 1 lock ofs=0 len=2: %d - %s",
+ ret, strerror(errno));
+ diag("process 1 took read lock on range 0,2");
+ send_char('a');
+ }
+
+ /* process2: F_RDLCK for ofs=0 len=1 */
+ if (process == 2) {
+ expect_char('a');
+ ret = raw_fcntl_lock(fd, F_RDLCK, 0, 1, true);
+ ok(ret == 0,
+ "process 2 lock ofs=0 len=1: %d - %s",
+ ret, strerror(errno));;
+ diag("process 2 took read lock on range 0,1");
+ send_char('b');
+ }
+
+ /* process1: upgrade ofs=0 len=2 to F_RWLCK (in blocking mode) */
+ if (process == 1) {
+ expect_char('b');
+ send_char('c');
+ diag("process 1 starts upgrade on range 0,2");
+ ret = raw_fcntl_lock(fd, F_WRLCK, 0, 2, true);
+ ok(ret == 0,
+ "process 1 RW lock ofs=0 len=2: %d - %s",
+ ret, strerror(errno));
+ diag("process 1 got read upgrade done");
+ /* at this point process 1 is blocked on 2 releasing the
+ read lock */
+ }
+
+ /*
+ * process2: F_RDLCK for ofs=1 len=1
+ * process2: unlock ofs=0 len=2
+ */
+ if (process == 2) {
+ expect_char('c'); /* we know process 1 is *about* to lock */
+ sleep(1);
+ ret = raw_fcntl_lock(fd, F_RDLCK, 1, 1, true);
+ ok(ret == 0,
+ "process 2 lock ofs=1 len=1: %d - %s",
+ ret, strerror(errno));
+ diag("process 2 got read lock on 1,1\n");
+ ret = raw_fcntl_unlock(fd, 0, 2);
+ ok(ret == 0,
+ "process 2 unlock ofs=0 len=2: %d - %s",
+ ret, strerror(errno));
+ diag("process 2 released read lock on 0,2\n");
+ sleep(1);
+ send_char('d');
+ }
+
+ if (process == 1) {
+ expect_char('d');
+ }
+
+ diag("process %d has got to the end\n", process);
+
+ return 0;
+}