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Subject[CHECKER] potential deadlocks
Date
Hi All,

here are a small number of potential deadlocks caught from a static
deadlock detector. It flags any places with locking cycles. E.g. it
will flag:

lock(a)
lock(b);
...
unlock(a);
unlock(b);
...
lock(b);
lock(a)
since a thread could grab "a" while another could grab "b" and then
both could spin waiting for the other's lock.

It understands that only the first read_lock and lock_kernel actually
does anything, so that it won't warn about

lock_kernel();
lock(a);
lock_kernel(); /* no lock acquired */

violating a partial order.

Any feedback on the results would be great. My understanding of linux's
sprawling locking rules is less than impressive. Also, if there are
known deadlocks, let me know and I can make sure we're finding them.

Note that the message format is a bit confusing. It prints out the number
of times each locking order occurred at and then gives some example paths.
For example, for the first error below:

<&driver_lock>-><&adap_lock> occurred 1 times
<&adap_lock>-><&driver_lock> occurred 1 times

means that driver_lock was aqcquired followed by adap_lock 1 time,
and the opposite also occured one time. A path to the first order
is given by:
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/i2c/i2c-core.c:i2c_del_driver:292
->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/i2c/i2c-core.c:i2c_del_driver:312

Thanks to Andrew for feedback on other race detector checker.

Dawson

--------------------------------------------------
BUG ERROR: 1 thread deadlock.
<&driver_lock>-><&adap_lock> occurred 1 times
<&adap_lock>-><&driver_lock> occurred 1 times
&driver_lock->&adap_lock =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/i2c/i2c-core.c:i2c_del_driver:292
->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/i2c/i2c-core.c:i2c_del_driver:312

&adap_lock->&driver_lock =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/i2c/i2c-core.c:i2c_del_adapter:175
->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/i2c/i2c-core.c:i2c_del_adapter:192

--------------------------------------------------
BUG ERROR: 1 thread deadlock.
<&rtc_lock>-><&rtc_task_lock> occurred 1 times
<&rtc_task_lock>-><&rtc_lock> occurred 1 times
&rtc_lock->&rtc_task_lock =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/char/rtc.c:rtc_register:723
->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/char/rtc.c:rtc_register:728

&rtc_task_lock->&rtc_lock =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/char/rtc.c:rtc_unregister:749
->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/char/rtc.c:rtc_unregister:755



--------------------------------------------------
BUG ERROR: 1 thread deadlock.
<struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.readmutex (<local>:0)>-><struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.mutex (<local>:0)> occurred 1 times
<struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.mutex (<local>:0)>-><struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.readmutex (<local>:0)> occurred 1 times
struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.readmutex (<local>:0)->struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.mutex (<local>:0) =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_read:1620
->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_read:1711

struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.mutex (<local>:0)->struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.readmutex (<local>:0) =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_read:1610
->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_read:1620

--------------------------------------------------
BUG ERROR: 1 thread deadlock.
<&dev_table_mutex>-><struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c162.mutex (<local>:0)> occurred 1 times
<struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c162.mutex (<local>:0)>-><&dev_table_mutex> occurred 1 times
&dev_table_mutex->struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c162.mutex (<local>:0) =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_open:1404
->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_open:1412

struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c162.mutex (<local>:0)->&dev_table_mutex =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerswald_disconnect:2091
->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerswald_disconnect:2096



--------------------------------------------------
BUG ERROR: 1 thread deadlock.
<lock_kernel>-><struct namespace.sem (<local>:0)> occurred 36 times
<struct namespace.sem (<local>:0)>-><lock_kernel> occurred 30 times
lock_kernel->struct namespace.sem (<local>:0) =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_pivot_root:974
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_pivot_root:997
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_umount:306
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_umount:335
depth = 3:
/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_mount:870
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_mount:870
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_mount:871
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_mount:753
->end=/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_loopback:511
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_loopback:511
depth = 3:
/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_mount:870
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_mount:870
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_mount:871
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_mount:755
->end=/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_move_mount:579
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_move_mount:579
depth = 3:
/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_mount:870
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_mount:870
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:sys_mount:871
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_mount:757
->end=/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_add_mount:644
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_add_mount:644

struct namespace.sem (<local>:0)->lock_kernel =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_umount:335
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/namespace.c:do_umount:341


--------------------------------------------------
BUG: ERROR: 1 thread deadlock.
<struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.readmutex (<local>:0)>-><struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.mutex (<local>:0)> occurred 1 times
<struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.mutex (<local>:0)>-><struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.readmutex (<local>:0)> occurred 1 times
struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.readmutex (<local>:0)->struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.mutex (<local>:0) =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_read:1620

/* only one reader per device allowed */
if (down_interruptible (&ccp->readmutex)) {
up (&ccp->mutex);

->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_read:1711

if (down_interruptible (&ccp->mutex)) {
up (&ccp->readmutex);


struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.mutex (<local>:0)->struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c582.readmutex (<local>:0) =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_read:1610

/* get the mutex */
if (down_interruptible (&ccp->mutex))
return -ERESTARTSYS;

->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_read:1620

/* only one reader per device allowed */
if (down_interruptible (&ccp->readmutex)) {
up (&ccp->mutex);



--------------------------------------------------
BUG: ERROR: 1 thread deadlock.
<&dev_table_mutex>-><struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c162.mutex (<local>:0)> occurred 1 times
<struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c162.mutex (<local>:0)>-><&dev_table_mutex> occurred 1 times
&dev_table_mutex->struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c162.mutex (<local>:0) =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerchar_open:1404
struct /u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c162.mutex (<local>:0)->&dev_table_mutex =

/* usb device available? */
if (down_interruptible (&dev_table_mutex)) {
return -ERESTARTSYS;
}
cp = dev_table[dtindex];
if (cp == NULL) {
up (&dev_table_mutex);
return -ENODEV;
}
if (down_interruptible (&cp->mutex)) {

depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerswald_disconnect:2091

->/u2/engler/mc/oses/linux/linux-2.5.62/drivers/usb/misc/auerswald.c:auerswald_disconnect:2096

down (&cp->mutex);
info ("device /dev/usb/%s now disconnecting", cp->name);

/* remove from device table */
/* Nobody can open() this device any more */
down (&dev_table_mutex);
dev_table[cp->dtindex] = NULL;
up (&dev_table_mutex);



--------------------------------------------------
BUG: ERROR: 1 thread deadlock.
<lock_kernel>-><struct block_device.bd_sem (<local>:0)> occurred 37 times
<struct block_device.bd_sem (<local>:0)>-><lock_kernel> occurred 36 times
lock_kernel->struct block_device.bd_sem (<local>:0) =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/fs/block_dev.c:do_open:569
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/block_dev.c:do_open:578

lock_kernel();
disk = get_gendisk(bdev->bd_dev, &part);
if (!disk) {
unlock_kernel();
bdput(bdev);
return ret;
}
owner = disk->fops->owner;

down(&bdev->bd_sem);

depth = 6:
/u2/engler/mc/oses/linux/linux-2.5.62/init/main.c:init:508
->/u2/engler/mc/oses/linux/linux-2.5.62/init/main.c:init:508
->/u2/engler/mc/oses/linux/linux-2.5.62/init/main.c:init:527
->/u2/engler/mc/oses/linux/linux-2.5.62/init/do_mounts.c:prepare_namespace:883
->/u2/engler/mc/oses/linux/linux-2.5.62/kernel/suspend.c:software_resume:1231
->/u2/engler/mc/oses/linux/linux-2.5.62/kernel/suspend.c:read_suspend_image:1170
->end=/u2/engler/mc/oses/linux/linux-2.5.62/fs/block_dev.c:blkdev_put:705
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/block_dev.c:blkdev_put:705

struct block_device.bd_sem (<local>:0)->lock_kernel =
depth = 1:
/u2/engler/mc/oses/linux/linux-2.5.62/fs/block_dev.c:blkdev_put:705
->/u2/engler/mc/oses/linux/linux-2.5.62/fs/block_dev.c:blkdev_put:712

down(&bdev->bd_sem);
switch (kind) {
case BDEV_FILE:
case BDEV_FS:
sync_blockdev(bd_inode->i_bdev);
break;
}
lock_kernel();

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