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#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;
}
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