On Thu, Apr 19 2007, Jens Axboe wrote:
> > Is it possible that fio was changed? That it was changed to close() the fd
> > before doing the munmapping whereas it used to hold the file open?
>
> It's been a while since I tested on this box, so I don't really recall.
> But fio does close() the fd before doing munmap(). This particular test
> case doesn't use mmap(), though.
Ah wait, but it does use mmap! Fio sets up a semaphore my mmap'ing a
file in /tmp (which is reiserfs). Here's a test case that triggers it
100% reliably, adjust /tmp to some other location that is reiserfs.
lockdep from that run attached.
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
int main(int argc, char *argv[])
{
char fname[] = "/tmp/some_file"; /* /tmp on reiserfs */
void *p;
int fd;
fd = open(fname, O_RDWR|O_CREAT, 0644);
if (fd < 0) {
perror("open");
return 1;
}
if (ftruncate(fd, 64) < 0) {
perror("ftruncate");
return 1;
}
p = mmap(NULL, 64, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
if (p == MAP_FAILED) {
perror("mmap");
return 1;
}
unlink(fname);
close(fd);
munmap(p, 64);
return 0;
}
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.21-rc7 #18
-------------------------------------------------------
reiser-mmap/9643 is trying to acquire lock:
(&inode->i_mutex){--..}, at: [<b038c625>] mutex_lock+0x1c/0x1f
but task is already holding lock:
(&mm->mmap_sem){----}, at: [<b015c6cf>] sys_munmap+0x26/0x42
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&mm->mmap_sem){----}:
[<b013e3fb>] __lock_acquire+0xdee/0xf9c
[<b013e600>] lock_acquire+0x57/0x70
[<b0137b92>] down_read+0x3a/0x4c
[<b01b6b88>] reiserfs_remount+0x176/0x42a
[<b016ba21>] do_remount_sb+0xb9/0x10f
[<b017ebe7>] do_mount+0x1b6/0x616
[<b017f0b6>] sys_mount+0x6f/0xa9
[<b0103f04>] sysenter_past_esp+0x5d/0x99
[<ffffffff>] 0xffffffff
-> #0 (&inode->i_mutex){--..}:
[<b013e259>] __lock_acquire+0xc4c/0xf9c
[<b013e600>] lock_acquire+0x57/0x70
[<b038c3e5>] __mutex_lock_slowpath+0x73/0x297
[<b038c625>] mutex_lock+0x1c/0x1f
[<b01b17e9>] reiserfs_file_release+0x54/0x447
[<b016afe7>] __fput+0x53/0x101
[<b016b0ee>] fput+0x19/0x1c
[<b015bcd5>] remove_vma+0x3b/0x4d
[<b015c659>] do_munmap+0x17f/0x1cf
[<b015c6db>] sys_munmap+0x32/0x42
[<b0103f04>] sysenter_past_esp+0x5d/0x99
[<ffffffff>] 0xffffffff
other info that might help us debug this:
1 lock held by reiser-mmap/9643:
#0: (&mm->mmap_sem){----}, at: [<b015c6cf>] sys_munmap+0x26/0x42
stack backtrace:
[<b0104f54>] show_trace_log_lvl+0x1a/0x30
[<b0105626>] show_trace+0x12/0x14
[<b01056ad>] dump_stack+0x16/0x18
[<b013c48d>] print_circular_bug_tail+0x68/0x71
[<b013e259>] __lock_acquire+0xc4c/0xf9c
[<b013e600>] lock_acquire+0x57/0x70
[<b038c3e5>] __mutex_lock_slowpath+0x73/0x297
[<b038c625>] mutex_lock+0x1c/0x1f
[<b01b17e9>] reiserfs_file_release+0x54/0x447
[<b016afe7>] __fput+0x53/0x101
[<b016b0ee>] fput+0x19/0x1c
[<b015bcd5>] remove_vma+0x3b/0x4d
[<b015c659>] do_munmap+0x17f/0x1cf
[<b015c6db>] sys_munmap+0x32/0x42
[<b0103f04>] sysenter_past_esp+0x5d/0x99
=======================
--
Jens Axboe
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