* DEBUG_RWSEMS warning from thaw_super()
@ 2018-05-13 14:02 Amir Goldstein
2018-05-13 16:04 ` Oleg Nesterov
0 siblings, 1 reply; 6+ messages in thread
From: Amir Goldstein @ 2018-05-13 14:02 UTC (permalink / raw)
To: Waiman Long
Cc: Ingo Molnar, linux-fsdevel, linux-kernel, Jan Kara,
Oleg Nesterov, Al Viro
Hi Waiman,
Since kernel v4.17-rc1 and DEBUG_RWSEMS, I see the
warning below after filesystem freeze/thaw.
This is a case where one process acquires a bunch of rwsem
and another process releases them.
To convey this use case to lockdep, freeze_super() calls
lockdep_sb_freeze_release() on exit and thaw_super()
calls lockdep_sb_freeze_acquire() on entry.
These annotations don't seem to have any effect on the
DEBUG_RWSEMS owner checks.
What do you think is the best way to resolve this issue?
Thanks,
Amir.
----------------------
root@kvm-xfstests:~# fsfreeze -f /vdf
root@kvm-xfstests:~# fsfreeze -u /vdf
[ 20.302978] ------------[ cut here ]------------
[ 20.305016] DEBUG_LOCKS_WARN_ON(sem->owner != get_current())
[ 20.305029] WARNING: CPU: 1 PID: 1401 at
/home/amir/build/src/linux/kernel/locking/rwsem.c:133
up_write+0x59/0x79
[ 20.311252] CPU: 1 PID: 1401 Comm: fsfreeze Not tainted
4.17.0-rc3-xfstests-00049-g39e47bf59eb3 #3276
[ 20.314808] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 20.318403] RIP: 0010:up_write+0x59/0x79
[ 20.320928] RSP: 0018:ffffc90000717e48 EFLAGS: 00010286
[ 20.322955] RAX: 0000000000000030 RBX: ffff880078f1c680 RCX: ffff880078e42200
[ 20.325665] RDX: ffffffff810cc9c1 RSI: 0000000000000001 RDI: 0000000000000202
[ 20.328844] RBP: ffffc90000717e80 R08: 0000000000000001 R09: 0000000000000001
[ 20.332340] R10: ffffc90000717c58 R11: ffffffff836807ad R12: ffff880078f1c388
[ 20.335095] R13: ffff880078a8b980 R14: 0000000000000000 R15: 00000000fffffff7
[ 20.338009] FS: 00007fb61ca42700(0000) GS:ffff88007f400000(0000)
knlGS:0000000000000000
[ 20.341423] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 20.343772] CR2: 00007fb61c559b30 CR3: 0000000078da6000 CR4: 00000000000006e0
[ 20.346463] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 20.349201] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 20.351960] Call Trace:
[ 20.352911] percpu_up_write+0x1f/0x28
[ 20.354344] thaw_super_locked+0xdf/0x120
[ 20.355944] do_vfs_ioctl+0x270/0x5f1
[ 20.357390] ? __se_sys_newfstat+0x2e/0x39
[ 20.358969] ? entry_SYSCALL_64_after_hwframe+0x59/0xbe
[ 20.360991] ksys_ioctl+0x52/0x71
[ 20.362384] __x64_sys_ioctl+0x16/0x19
[ 20.363702] do_syscall_64+0x5d/0x167
[ 20.365099] entry_SYSCALL_64_after_hwframe+0x49/0xbe
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: DEBUG_RWSEMS warning from thaw_super()
2018-05-13 14:02 DEBUG_RWSEMS warning from thaw_super() Amir Goldstein
@ 2018-05-13 16:04 ` Oleg Nesterov
2018-05-14 9:50 ` Jan Kara
0 siblings, 1 reply; 6+ messages in thread
From: Oleg Nesterov @ 2018-05-13 16:04 UTC (permalink / raw)
To: Amir Goldstein
Cc: Waiman Long, Ingo Molnar, linux-fsdevel, linux-kernel, Jan Kara, Al Viro
On 05/13, Amir Goldstein wrote:
>
> Since kernel v4.17-rc1 and DEBUG_RWSEMS, I see the
> warning below after filesystem freeze/thaw.
>
> This is a case where one process acquires a bunch of rwsem
> and another process releases them.
>
> To convey this use case to lockdep, freeze_super() calls
> lockdep_sb_freeze_release() on exit and thaw_super()
> calls lockdep_sb_freeze_acquire() on entry.
This was already discussed, but I forgot the result...
So once again, why we can't simply update percpu_rwsem_acquire() ?
Or we can check CONFIG_RWSEM_SPIN_ON_OWNER to match percpu_rwsem_release(),
but CONFIG_DEBUG_RWSEMS explains the purpose better.
Oleg.
--- x/include/linux/percpu-rwsem.h
+++ x/include/linux/percpu-rwsem.h
@@ -141,6 +141,10 @@ static inline void percpu_rwsem_acquire(
bool read, unsigned long ip)
{
lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
+#ifdef CONFIG_DEBUG_RWSEMS
+ if (!read)
+ sem->rw_sem.owner = current;
+#endif
}
#endif
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: DEBUG_RWSEMS warning from thaw_super()
2018-05-13 16:04 ` Oleg Nesterov
@ 2018-05-14 9:50 ` Jan Kara
2018-05-14 11:32 ` Amir Goldstein
0 siblings, 1 reply; 6+ messages in thread
From: Jan Kara @ 2018-05-14 9:50 UTC (permalink / raw)
To: Oleg Nesterov
Cc: Amir Goldstein, Waiman Long, Ingo Molnar, linux-fsdevel,
linux-kernel, Jan Kara, Al Viro
On Sun 13-05-18 18:04:04, Oleg Nesterov wrote:
> On 05/13, Amir Goldstein wrote:
> >
> > Since kernel v4.17-rc1 and DEBUG_RWSEMS, I see the
> > warning below after filesystem freeze/thaw.
> >
> > This is a case where one process acquires a bunch of rwsem
> > and another process releases them.
> >
> > To convey this use case to lockdep, freeze_super() calls
> > lockdep_sb_freeze_release() on exit and thaw_super()
> > calls lockdep_sb_freeze_acquire() on entry.
>
> This was already discussed, but I forgot the result...
>
> So once again, why we can't simply update percpu_rwsem_acquire() ?
> Or we can check CONFIG_RWSEM_SPIN_ON_OWNER to match percpu_rwsem_release(),
> but CONFIG_DEBUG_RWSEMS explains the purpose better.
Yeah, what you suggests seems reasonable to me. So feel free to add:
Acked-by: Jan Kara <jack@suse.cz>
Honza
> --- x/include/linux/percpu-rwsem.h
> +++ x/include/linux/percpu-rwsem.h
> @@ -141,6 +141,10 @@ static inline void percpu_rwsem_acquire(
> bool read, unsigned long ip)
> {
> lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
> +#ifdef CONFIG_DEBUG_RWSEMS
> + if (!read)
> + sem->rw_sem.owner = current;
> +#endif
> }
>
> #endif
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: DEBUG_RWSEMS warning from thaw_super()
2018-05-14 9:50 ` Jan Kara
@ 2018-05-14 11:32 ` Amir Goldstein
2018-05-14 11:51 ` Oleg Nesterov
0 siblings, 1 reply; 6+ messages in thread
From: Amir Goldstein @ 2018-05-14 11:32 UTC (permalink / raw)
To: Jan Kara
Cc: Oleg Nesterov, Waiman Long, Ingo Molnar, linux-fsdevel,
linux-kernel, Al Viro
On Mon, May 14, 2018 at 12:50 PM, Jan Kara <jack@suse.cz> wrote:
> On Sun 13-05-18 18:04:04, Oleg Nesterov wrote:
>> On 05/13, Amir Goldstein wrote:
>> >
>> > Since kernel v4.17-rc1 and DEBUG_RWSEMS, I see the
>> > warning below after filesystem freeze/thaw.
>> >
>> > This is a case where one process acquires a bunch of rwsem
>> > and another process releases them.
>> >
>> > To convey this use case to lockdep, freeze_super() calls
>> > lockdep_sb_freeze_release() on exit and thaw_super()
>> > calls lockdep_sb_freeze_acquire() on entry.
>>
>> This was already discussed, but I forgot the result...
>>
>> So once again, why we can't simply update percpu_rwsem_acquire() ?
>> Or we can check CONFIG_RWSEM_SPIN_ON_OWNER to match percpu_rwsem_release(),
>> but CONFIG_DEBUG_RWSEMS explains the purpose better.
>
> Yeah, what you suggests seems reasonable to me. So feel free to add:
>
> Acked-by: Jan Kara <jack@suse.cz>
>
How about this version? A bit more prudent and also addresses the
TODO in commit 55cc156505f2 ("percpu-rwsem: introduce
percpu_rwsem_release() and percpu_rwsem_acquire()")
Sorry for spaces instead of tabs, I'll re-post properly if this is acked.
Thanks,
Amir.
-----
diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index b1f37a89e368..323d5ba6a60d 100644
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -127,13 +127,16 @@ extern void percpu_free_rwsem(struct
percpu_rw_semaphore *);
#define percpu_rwsem_assert_held(sem) \
lockdep_assert_held(&(sem)->rw_sem)
+extern void percpu_rwsem_set_user_owned(struct percpu_rw_semaphore *sem);
+extern void percpu_rwsem_set_owner(struct percpu_rw_semaphore *sem);
+
static inline void percpu_rwsem_release(struct percpu_rw_semaphore *sem,
bool read, unsigned long ip)
{
lock_release(&sem->rw_sem.dep_map, 1, ip);
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
if (!read)
- sem->rw_sem.owner = NULL;
+ percpu_rwsem_set_user_owned(sem);
#endif
}
@@ -141,6 +144,10 @@ static inline void percpu_rwsem_acquire(struct
percpu_rw_semaphore *sem,
bool read, unsigned long ip)
{
lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+ if (!read)
+ percpu_rwsem_set_owner(sem);
+#endif
}
#endif
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 883cf1b92d90..afa65915541f 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -7,6 +7,8 @@
#include <linux/sched.h>
#include <linux/errno.h>
+#include "rwsem.h"
+
int __percpu_init_rwsem(struct percpu_rw_semaphore *sem,
const char *name, struct lock_class_key *rwsem_key)
{
@@ -190,3 +192,17 @@ void percpu_up_write(struct percpu_rw_semaphore *sem)
rcu_sync_exit(&sem->rss);
}
EXPORT_SYMBOL_GPL(percpu_up_write);
+
+void percpu_rwsem_set_user_owned(struct percpu_rw_semaphore *sem)
+{
+ DEBUG_RWSEMS_WARN_ON(sem->rw_sem.owner != current);
+ sem->rw_sem.owner = RWSEM_USER_OWNED;
+}
+EXPORT_SYMBOL_GPL(percpu_rwsem_set_user_owned);
+
+void percpu_rwsem_set_owner(struct percpu_rw_semaphore *sem)
+{
+ DEBUG_RWSEMS_WARN_ON(sem->rw_sem.owner != RWSEM_USER_OWNED);
+ sem->rw_sem.owner = current;
+}
+EXPORT_SYMBOL_GPL(percpu_rwsem_set_user_owned);
diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h
index a17cba8d94bb..f686596ec033 100644
--- a/kernel/locking/rwsem.h
+++ b/kernel/locking/rwsem.h
@@ -11,10 +11,14 @@
* 2) RWSEM_READER_OWNED
* - lock is currently or previously owned by readers (lock is free
* or not set by owner yet)
- * 3) Other non-zero value
+ * 3) RWSEM_USER_OWNED
+ * - lock is currently owned by userspace (previously owned by writer
+ * and should be handed over to a new writer before being freed)
+ * 4) Other non-zero value
* - a writer owns the lock
*/
#define RWSEM_READER_OWNED ((struct task_struct *)1UL)
+#define RWSEM_USER_OWNED ((struct task_struct *)2UL)
#ifdef CONFIG_DEBUG_RWSEMS
# define DEBUG_RWSEMS_WARN_ON(c) DEBUG_LOCKS_WARN_ON(c)
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: DEBUG_RWSEMS warning from thaw_super()
2018-05-14 11:32 ` Amir Goldstein
@ 2018-05-14 11:51 ` Oleg Nesterov
2018-05-14 12:16 ` Amir Goldstein
0 siblings, 1 reply; 6+ messages in thread
From: Oleg Nesterov @ 2018-05-14 11:51 UTC (permalink / raw)
To: Amir Goldstein
Cc: Jan Kara, Waiman Long, Ingo Molnar, linux-fsdevel, linux-kernel, Al Viro
On 05/14, Amir Goldstein wrote:
>
> On Mon, May 14, 2018 at 12:50 PM, Jan Kara <jack@suse.cz> wrote:
> > On Sun 13-05-18 18:04:04, Oleg Nesterov wrote:
> >> On 05/13, Amir Goldstein wrote:
> >> >
> >> > Since kernel v4.17-rc1 and DEBUG_RWSEMS, I see the
> >> > warning below after filesystem freeze/thaw.
> >> >
> >> > This is a case where one process acquires a bunch of rwsem
> >> > and another process releases them.
> >> >
> >> > To convey this use case to lockdep, freeze_super() calls
> >> > lockdep_sb_freeze_release() on exit and thaw_super()
> >> > calls lockdep_sb_freeze_acquire() on entry.
> >>
> >> This was already discussed, but I forgot the result...
> >>
> >> So once again, why we can't simply update percpu_rwsem_acquire() ?
> >> Or we can check CONFIG_RWSEM_SPIN_ON_OWNER to match percpu_rwsem_release(),
> >> but CONFIG_DEBUG_RWSEMS explains the purpose better.
> >
> > Yeah, what you suggests seems reasonable to me. So feel free to add:
> >
> > Acked-by: Jan Kara <jack@suse.cz>
> >
>
> How about this version? A bit more prudent and also addresses the
> TODO in commit 55cc156505f2 ("percpu-rwsem: introduce
> percpu_rwsem_release() and percpu_rwsem_acquire()")
Well, to me this looks like unnecessary overcomplication...
In any case the patch looks technically wrong, afaics
rwsem_can_spin_on_owner() will crash if it hits owner == RWSEM_USER_OWNED.
Oleg.
> diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
> index b1f37a89e368..323d5ba6a60d 100644
> --- a/include/linux/percpu-rwsem.h
> +++ b/include/linux/percpu-rwsem.h
> @@ -127,13 +127,16 @@ extern void percpu_free_rwsem(struct
> percpu_rw_semaphore *);
> #define percpu_rwsem_assert_held(sem) \
> lockdep_assert_held(&(sem)->rw_sem)
>
> +extern void percpu_rwsem_set_user_owned(struct percpu_rw_semaphore *sem);
> +extern void percpu_rwsem_set_owner(struct percpu_rw_semaphore *sem);
> +
> static inline void percpu_rwsem_release(struct percpu_rw_semaphore *sem,
> bool read, unsigned long ip)
> {
> lock_release(&sem->rw_sem.dep_map, 1, ip);
> #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
> if (!read)
> - sem->rw_sem.owner = NULL;
> + percpu_rwsem_set_user_owned(sem);
> #endif
> }
>
> @@ -141,6 +144,10 @@ static inline void percpu_rwsem_acquire(struct
> percpu_rw_semaphore *sem,
> bool read, unsigned long ip)
> {
> lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
> +#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
> + if (!read)
> + percpu_rwsem_set_owner(sem);
> +#endif
> }
>
> #endif
> diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
> index 883cf1b92d90..afa65915541f 100644
> --- a/kernel/locking/percpu-rwsem.c
> +++ b/kernel/locking/percpu-rwsem.c
> @@ -7,6 +7,8 @@
> #include <linux/sched.h>
> #include <linux/errno.h>
>
> +#include "rwsem.h"
> +
> int __percpu_init_rwsem(struct percpu_rw_semaphore *sem,
> const char *name, struct lock_class_key *rwsem_key)
> {
> @@ -190,3 +192,17 @@ void percpu_up_write(struct percpu_rw_semaphore *sem)
> rcu_sync_exit(&sem->rss);
> }
> EXPORT_SYMBOL_GPL(percpu_up_write);
> +
> +void percpu_rwsem_set_user_owned(struct percpu_rw_semaphore *sem)
> +{
> + DEBUG_RWSEMS_WARN_ON(sem->rw_sem.owner != current);
> + sem->rw_sem.owner = RWSEM_USER_OWNED;
> +}
> +EXPORT_SYMBOL_GPL(percpu_rwsem_set_user_owned);
> +
> +void percpu_rwsem_set_owner(struct percpu_rw_semaphore *sem)
> +{
> + DEBUG_RWSEMS_WARN_ON(sem->rw_sem.owner != RWSEM_USER_OWNED);
> + sem->rw_sem.owner = current;
> +}
> +EXPORT_SYMBOL_GPL(percpu_rwsem_set_user_owned);
> diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h
> index a17cba8d94bb..f686596ec033 100644
> --- a/kernel/locking/rwsem.h
> +++ b/kernel/locking/rwsem.h
> @@ -11,10 +11,14 @@
> * 2) RWSEM_READER_OWNED
> * - lock is currently or previously owned by readers (lock is free
> * or not set by owner yet)
> - * 3) Other non-zero value
> + * 3) RWSEM_USER_OWNED
> + * - lock is currently owned by userspace (previously owned by writer
> + * and should be handed over to a new writer before being freed)
> + * 4) Other non-zero value
> * - a writer owns the lock
> */
> #define RWSEM_READER_OWNED ((struct task_struct *)1UL)
> +#define RWSEM_USER_OWNED ((struct task_struct *)2UL)
>
> #ifdef CONFIG_DEBUG_RWSEMS
> # define DEBUG_RWSEMS_WARN_ON(c) DEBUG_LOCKS_WARN_ON(c)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: DEBUG_RWSEMS warning from thaw_super()
2018-05-14 11:51 ` Oleg Nesterov
@ 2018-05-14 12:16 ` Amir Goldstein
0 siblings, 0 replies; 6+ messages in thread
From: Amir Goldstein @ 2018-05-14 12:16 UTC (permalink / raw)
To: Oleg Nesterov
Cc: Jan Kara, Waiman Long, Ingo Molnar, linux-fsdevel, linux-kernel, Al Viro
On Mon, May 14, 2018 at 2:51 PM, Oleg Nesterov <oleg@redhat.com> wrote:
> On 05/14, Amir Goldstein wrote:
>>
>> On Mon, May 14, 2018 at 12:50 PM, Jan Kara <jack@suse.cz> wrote:
>> > On Sun 13-05-18 18:04:04, Oleg Nesterov wrote:
>> >> On 05/13, Amir Goldstein wrote:
>> >> >
>> >> > Since kernel v4.17-rc1 and DEBUG_RWSEMS, I see the
>> >> > warning below after filesystem freeze/thaw.
>> >> >
>> >> > This is a case where one process acquires a bunch of rwsem
>> >> > and another process releases them.
>> >> >
>> >> > To convey this use case to lockdep, freeze_super() calls
>> >> > lockdep_sb_freeze_release() on exit and thaw_super()
>> >> > calls lockdep_sb_freeze_acquire() on entry.
>> >>
>> >> This was already discussed, but I forgot the result...
>> >>
>> >> So once again, why we can't simply update percpu_rwsem_acquire() ?
>> >> Or we can check CONFIG_RWSEM_SPIN_ON_OWNER to match percpu_rwsem_release(),
>> >> but CONFIG_DEBUG_RWSEMS explains the purpose better.
>> >
>> > Yeah, what you suggests seems reasonable to me. So feel free to add:
>> >
>> > Acked-by: Jan Kara <jack@suse.cz>
>> >
>>
>> How about this version? A bit more prudent and also addresses the
>> TODO in commit 55cc156505f2 ("percpu-rwsem: introduce
>> percpu_rwsem_release() and percpu_rwsem_acquire()")
>
> Well, to me this looks like unnecessary overcomplication...
>
> In any case the patch looks technically wrong, afaics
> rwsem_can_spin_on_owner() will crash if it hits owner == RWSEM_USER_OWNED.
>
Fair enough. I can drop RWSEM_USER_OWNED.
Do you think I should keep percpu_rwsem_{set,clear}_owner()
helpers?
Thanks,
Amir.
> Oleg.
>
>> diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
>> index b1f37a89e368..323d5ba6a60d 100644
>> --- a/include/linux/percpu-rwsem.h
>> +++ b/include/linux/percpu-rwsem.h
>> @@ -127,13 +127,16 @@ extern void percpu_free_rwsem(struct
>> percpu_rw_semaphore *);
>> #define percpu_rwsem_assert_held(sem) \
>> lockdep_assert_held(&(sem)->rw_sem)
>>
>> +extern void percpu_rwsem_set_user_owned(struct percpu_rw_semaphore *sem);
>> +extern void percpu_rwsem_set_owner(struct percpu_rw_semaphore *sem);
>> +
>> static inline void percpu_rwsem_release(struct percpu_rw_semaphore *sem,
>> bool read, unsigned long ip)
>> {
>> lock_release(&sem->rw_sem.dep_map, 1, ip);
>> #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
>> if (!read)
>> - sem->rw_sem.owner = NULL;
>> + percpu_rwsem_set_user_owned(sem);
>> #endif
>> }
>>
>> @@ -141,6 +144,10 @@ static inline void percpu_rwsem_acquire(struct
>> percpu_rw_semaphore *sem,
>> bool read, unsigned long ip)
>> {
>> lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
>> +#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
>> + if (!read)
>> + percpu_rwsem_set_owner(sem);
>> +#endif
>> }
>>
>> #endif
>> diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
>> index 883cf1b92d90..afa65915541f 100644
>> --- a/kernel/locking/percpu-rwsem.c
>> +++ b/kernel/locking/percpu-rwsem.c
>> @@ -7,6 +7,8 @@
>> #include <linux/sched.h>
>> #include <linux/errno.h>
>>
>> +#include "rwsem.h"
>> +
>> int __percpu_init_rwsem(struct percpu_rw_semaphore *sem,
>> const char *name, struct lock_class_key *rwsem_key)
>> {
>> @@ -190,3 +192,17 @@ void percpu_up_write(struct percpu_rw_semaphore *sem)
>> rcu_sync_exit(&sem->rss);
>> }
>> EXPORT_SYMBOL_GPL(percpu_up_write);
>> +
>> +void percpu_rwsem_set_user_owned(struct percpu_rw_semaphore *sem)
>> +{
>> + DEBUG_RWSEMS_WARN_ON(sem->rw_sem.owner != current);
>> + sem->rw_sem.owner = RWSEM_USER_OWNED;
>> +}
>> +EXPORT_SYMBOL_GPL(percpu_rwsem_set_user_owned);
>> +
>> +void percpu_rwsem_set_owner(struct percpu_rw_semaphore *sem)
>> +{
>> + DEBUG_RWSEMS_WARN_ON(sem->rw_sem.owner != RWSEM_USER_OWNED);
>> + sem->rw_sem.owner = current;
>> +}
>> +EXPORT_SYMBOL_GPL(percpu_rwsem_set_user_owned);
>> diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h
>> index a17cba8d94bb..f686596ec033 100644
>> --- a/kernel/locking/rwsem.h
>> +++ b/kernel/locking/rwsem.h
>> @@ -11,10 +11,14 @@
>> * 2) RWSEM_READER_OWNED
>> * - lock is currently or previously owned by readers (lock is free
>> * or not set by owner yet)
>> - * 3) Other non-zero value
>> + * 3) RWSEM_USER_OWNED
>> + * - lock is currently owned by userspace (previously owned by writer
>> + * and should be handed over to a new writer before being freed)
>> + * 4) Other non-zero value
>> * - a writer owns the lock
>> */
>> #define RWSEM_READER_OWNED ((struct task_struct *)1UL)
>> +#define RWSEM_USER_OWNED ((struct task_struct *)2UL)
>>
>> #ifdef CONFIG_DEBUG_RWSEMS
>> # define DEBUG_RWSEMS_WARN_ON(c) DEBUG_LOCKS_WARN_ON(c)
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-05-14 12:16 UTC | newest]
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2018-05-13 14:02 DEBUG_RWSEMS warning from thaw_super() Amir Goldstein
2018-05-13 16:04 ` Oleg Nesterov
2018-05-14 9:50 ` Jan Kara
2018-05-14 11:32 ` Amir Goldstein
2018-05-14 11:51 ` Oleg Nesterov
2018-05-14 12:16 ` Amir Goldstein
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