Messages in this thread Patches in this message | | | Date | Thu, 19 Oct 2006 02:15:06 +0400 | From | Anton Vorontsov <> | Subject | [PATCH] genhd fix or ide workaround -- choose one |
| |
Hi all,
I've caught deadlock inside IDE layer using IDE-CS: after accessing to IDE disk placed in PCMCIA (CF card really), it will never probe again after pulling it from PCMCIA/CF.
The kernel is stuck at drivers/ide/ide.c:ide_unregister():604:
602 spin_unlock_irq(&ide_lock); 603 device_unregister(&drive->gendev); 604 wait_for_completion(&drive->gendev_rel_comp); 605 spin_lock_irq(&ide_lock);
ide_unregister() assumes that device_unregister() will call ide-probe.c:drive_release_dev():
1282 static void drive_release_dev (struct device *dev) 1283 { .... [...] 1302 complete(&drive->gendev_rel_comp); 1303 }
1311 static void init_gendisk (ide_hwif_t *hwif) 1312 { .... 1323 drive->gendev.release = drive_release_dev; .... 1333 }
But release() function will not called because drive->gendev is still referenced inside genhd layer.
I'm attaching two patches: the fix and the workaround. I assume that first is a candidate to -mm, and workaround is a temporary solution.
There are two set of patches: for the Linus's git tree and for the handhelds.org's 2.6.17-hh1 (prefixed with hh-).
Note: this is cross-posting, thus please keep To: and CC: headers, to keep us all in sync.
Thanks,
-- Anton (irc: bd2) From: Anton Vorontsov <cbou@mail.ru>
No need to get_device(driverfs_dev), because it's already gotten by add_disk(). And no function will call put_device() second time. This is the source of deadlock[1] in IDE layer. SCSI workaround it by calling put_device() themself after put_disk(), thus it should reflect this change by removing put_device().
[1] deadlock in ide_unregister() at wait_for_completion(&drive->gendev_rel_comp) after device_unregister(&drive->gendev). That happens by reason of ide-probe.c:drive_release_dev() not called because of driverfs_dev (which is drive->gendev) still referenced by add_disk().
diff --git a/fs/partitions/check.c b/fs/partitions/check.c index 6fb4b61..8371adf 100644 --- a/fs/partitions/check.c +++ b/fs/partitions/check.c @@ -378,7 +378,7 @@ static char *make_block_name(struct gend static int disk_sysfs_symlinks(struct gendisk *disk) { - struct device *target = get_device(disk->driverfs_dev); + struct device *target = disk->driverfs_dev; int err; char *disk_name = NULL; @@ -414,9 +414,8 @@ err_out_dev_link: sysfs_remove_link(&disk->kobj, "device"); err_out_disk_name: kfree(disk_name); -err_out: - put_device(target); } +err_out: return err; } diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index 84ff203..03dca98 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -1760,7 +1760,6 @@ static void scsi_disk_release(struct cla disk->private_data = NULL; put_disk(disk); - put_device(&sdkp->device->sdev_gendev); kfree(sdkp); }From: Anton Vorontsov <cbou@mail.ru>
Because add_disk() getting driverfs_dev twice but putting it only once, ide-{disk,cd,floppy} should put_device() themselfs. This is workaround for the bug found in genhd, which causes deadlock in ide_unregister() at wait_for_completion(&drive->gendev_rel_comp) after device_unregister(&drive->gendev). That happens by reason of ide-probe.c:drive_release_dev() not called because of driverfs_dev (which is drive->gendev) still referenced by add_disk().
diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c index bddfebd..59121a3 100644 --- a/drivers/ide/ide-cd.c +++ b/drivers/ide/ide-cd.c @@ -3307,6 +3307,7 @@ static void ide_cd_release(struct kref * blk_queue_prep_rq(drive->queue, NULL); g->private_data = NULL; put_disk(g); + put_device(&drive->gendev); kfree(info); } diff --git a/drivers/ide/ide-disk.c b/drivers/ide/ide-disk.c index 0a05a37..d5d02a1 100644 --- a/drivers/ide/ide-disk.c +++ b/drivers/ide/ide-disk.c @@ -1020,6 +1020,7 @@ static void ide_disk_release(struct kref drive->driver_data = NULL; g->private_data = NULL; put_disk(g); + put_device(&drive->gendev); kfree(idkp); } diff --git a/drivers/ide/ide-floppy.c b/drivers/ide/ide-floppy.c index 8ccee9c..7a60d8c 100644 --- a/drivers/ide/ide-floppy.c +++ b/drivers/ide/ide-floppy.c @@ -1887,6 +1887,7 @@ static void ide_floppy_release(struct kr drive->driver_data = NULL; g->private_data = NULL; put_disk(g); + put_device(&drive->gendev); kfree(floppy); } From: Anton Vorontsov <cbou@mail.ru>
No need to get_device(driverfs_dev), because it's already gotten by add_disk(). And no function will call put_device() second time. This is the source of deadlock[1] in IDE layer. SCSI workaround it by calling put_device() themself after put_disk(), thus it should reflect this change by removing put_device().
[1] deadlock in ide_unregister() at wait_for_completion(&drive->gendev_rel_comp) after device_unregister(&drive->gendev). That happens by reason of ide-probe.c:drive_release_dev() not called because of driverfs_dev (which is drive->gendev) still referenced by add_disk().
Index: fs/partitions/check.c =================================================================== RCS file: /cvs/linux/kernel26/fs/partitions/check.c,v retrieving revision 1.17 diff -u -p -b -B -r1.17 check.c --- fs/partitions/check.c 23 Aug 2006 18:40:39 -0000 1.17 +++ fs/partitions/check.c 18 Oct 2006 21:13:26 -0000 @@ -389,7 +389,7 @@ static char *make_block_name(struct gend static void disk_sysfs_symlinks(struct gendisk *disk) { - struct device *target = get_device(disk->driverfs_dev); + struct device *target = disk->driverfs_dev; if (target) { char *disk_name = make_block_name(disk); sysfs_create_link(&disk->kobj,&target->kobj,"device"); Index: drivers/scsi/sd.c =================================================================== RCS file: /cvs/linux/kernel26/drivers/scsi/sd.c,v retrieving revision 1.18 diff -u -p -b -B -r1.18 sd.c --- drivers/scsi/sd.c 23 Aug 2006 18:38:06 -0000 1.18 +++ drivers/scsi/sd.c 18 Oct 2006 21:14:54 -0000 @@ -1756,7 +1756,6 @@ static void scsi_disk_release(struct cla disk->private_data = NULL; put_disk(disk); - put_device(&sdkp->device->sdev_gendev); kfree(sdkp); }From: Anton Vorontsov <cbou@mail.ru>
Because add_disk() getting driverfs_dev twice but putting it only once, ide-{disk,cd,floppy} should put_device() themselfs. This is workaround for the bug found in genhd, which causes deadlock in ide_unregister() at wait_for_completion(&drive->gendev_rel_comp) after device_unregister(&drive->gendev). That happens by reason of ide-probe.c:drive_release_dev() not called because of driverfs_dev (which is drive->gendev) still referenced by add_disk().
Index: drivers/ide/ide-cd.c =================================================================== RCS file: /cvs/linux/kernel26/drivers/ide/ide-cd.c,v retrieving revision 1.21 diff -u -p -b -B -r1.21 ide-cd.c --- drivers/ide/ide-cd.c 23 Aug 2006 18:35:05 -0000 1.21 +++ drivers/ide/ide-cd.c 18 Oct 2006 21:18:52 -0000 @@ -3240,6 +3240,7 @@ static void ide_cd_release(struct kref * blk_queue_prep_rq(drive->queue, NULL); g->private_data = NULL; put_disk(g); + put_device(&drive->gendev); kfree(info); } Index: drivers/ide/ide-disk.c =================================================================== RCS file: /cvs/linux/kernel26/drivers/ide/ide-disk.c,v retrieving revision 1.19 diff -u -p -b -B -r1.19 ide-disk.c --- drivers/ide/ide-disk.c 23 Aug 2006 18:35:05 -0000 1.19 +++ drivers/ide/ide-disk.c 18 Oct 2006 21:18:52 -0000 @@ -1021,6 +1021,7 @@ static void ide_disk_release(struct kref drive->devfs_name[0] = '\0'; g->private_data = NULL; put_disk(g); + put_device(&drive->gendev); kfree(idkp); } Index: drivers/ide/ide-floppy.c =================================================================== RCS file: /cvs/linux/kernel26/drivers/ide/ide-floppy.c,v retrieving revision 1.16 diff -u -p -b -B -r1.16 ide-floppy.c --- drivers/ide/ide-floppy.c 23 Aug 2006 18:35:05 -0000 1.16 +++ drivers/ide/ide-floppy.c 18 Oct 2006 21:18:52 -0000 @@ -1893,6 +1893,7 @@ static void ide_floppy_release(struct kr drive->driver_data = NULL; g->private_data = NULL; put_disk(g); + put_device(&drive->gendev); kfree(floppy); } | |