* [PATCH 2.6.35-rc3] Add RCU check for find_task_by_vpid().
@ 2010-06-25 16:08 Tetsuo Handa
2010-06-25 17:48 ` Paul E. McKenney
0 siblings, 1 reply; 4+ messages in thread
From: Tetsuo Handa @ 2010-06-25 16:08 UTC (permalink / raw)
To: paulmck, mingo; +Cc: linux-kernel
find_task_by_vpid() says "Must be called under rcu_read_lock().". But due to
commit 3120438 "rcu: Disable lockdep checking in RCU list-traversal primitives",
we are currently unable to catch "find_task_by_vpid() with tasklist_lock held
but RCU lock not held" errors.
===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
kernel/pid.c:386 invoked rcu_dereference_check() without protection!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 1
1 lock held by rc.sysinit/1102:
#0: (tasklist_lock){.+.+..}, at: [<c1048340>] sys_setpgid+0x40/0x160
stack backtrace:
Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1
Call Trace:
[<c105e714>] lockdep_rcu_dereference+0x94/0xb0
[<c104b4cd>] find_task_by_pid_ns+0x6d/0x70
[<c104b4e8>] find_task_by_vpid+0x18/0x20
[<c1048347>] sys_setpgid+0x47/0x160
[<c1002b50>] sysenter_do_call+0x12/0x36
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
diff --git a/kernel/pid.c b/kernel/pid.c
index e9fd8c1..a257471 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -382,6 +382,9 @@ EXPORT_SYMBOL(pid_task);
*/
struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
{
+#ifdef __do_rcu_dereference_check
+ __do_rcu_dereference_check(rcu_read_lock_held());
+#endif
return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
}
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH 2.6.35-rc3] Add RCU check for find_task_by_vpid().
2010-06-25 16:08 [PATCH 2.6.35-rc3] Add RCU check for find_task_by_vpid() Tetsuo Handa
@ 2010-06-25 17:48 ` Paul E. McKenney
2010-06-25 22:41 ` Tetsuo Handa
0 siblings, 1 reply; 4+ messages in thread
From: Paul E. McKenney @ 2010-06-25 17:48 UTC (permalink / raw)
To: Tetsuo Handa; +Cc: mingo, linux-kernel
On Sat, Jun 26, 2010 at 01:08:19AM +0900, Tetsuo Handa wrote:
> find_task_by_vpid() says "Must be called under rcu_read_lock().". But due to
> commit 3120438 "rcu: Disable lockdep checking in RCU list-traversal primitives",
> we are currently unable to catch "find_task_by_vpid() with tasklist_lock held
> but RCU lock not held" errors.
>
> ===================================================
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> kernel/pid.c:386 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 1, debug_locks = 1
> 1 lock held by rc.sysinit/1102:
> #0: (tasklist_lock){.+.+..}, at: [<c1048340>] sys_setpgid+0x40/0x160
>
> stack backtrace:
> Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1
> Call Trace:
> [<c105e714>] lockdep_rcu_dereference+0x94/0xb0
> [<c104b4cd>] find_task_by_pid_ns+0x6d/0x70
> [<c104b4e8>] find_task_by_vpid+0x18/0x20
> [<c1048347>] sys_setpgid+0x47/0x160
> [<c1002b50>] sysenter_do_call+0x12/0x36
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
> diff --git a/kernel/pid.c b/kernel/pid.c
> index e9fd8c1..a257471 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -382,6 +382,9 @@ EXPORT_SYMBOL(pid_task);
> */
> struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
> {
> +#ifdef __do_rcu_dereference_check
> + __do_rcu_dereference_check(rcu_read_lock_held());
> +#endif
How about the following?
WARN_ON_ONCE(!rcu_read_lock_held());
> return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
> }
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH 2.6.35-rc3] Add RCU check for find_task_by_vpid().
2010-06-25 17:48 ` Paul E. McKenney
@ 2010-06-25 22:41 ` Tetsuo Handa
2010-06-28 23:41 ` Paul E. McKenney
0 siblings, 1 reply; 4+ messages in thread
From: Tetsuo Handa @ 2010-06-25 22:41 UTC (permalink / raw)
To: paulmck; +Cc: mingo, linux-kernel
Hello.
Paul E. McKenney wrote:
> > diff --git a/kernel/pid.c b/kernel/pid.c
> > index e9fd8c1..a257471 100644
> > --- a/kernel/pid.c
> > +++ b/kernel/pid.c
> > @@ -382,6 +382,9 @@ EXPORT_SYMBOL(pid_task);
> > */
> > struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
> > {
> > +#ifdef __do_rcu_dereference_check
> > + __do_rcu_dereference_check(rcu_read_lock_held());
> > +#endif
>
> How about the following?
>
> WARN_ON_ONCE(!rcu_read_lock_held());
>
> > return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
> > }
> >
Fine by me if you don't mind WARN_ON_ONCE(!1); for CONFIG_DEBUG_LOCK_ALLOC=n .
Personally,
> > ===================================================
> > [ INFO: suspicious rcu_dereference_check() usage. ]
> > ---------------------------------------------------
> > kernel/pid.c:386 invoked rcu_dereference_check() without protection!
> >
> > other info that might help us debug this:
> >
> >
> > rcu_scheduler_active = 1, debug_locks = 1
> > 1 lock held by rc.sysinit/1102:
> > #0: (tasklist_lock){.+.+..}, at: [<c1048340>] sys_setpgid+0x40/0x160
> >
> > stack backtrace:
> > Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1
> > Call Trace:
> > [<c105e714>] lockdep_rcu_dereference+0x94/0xb0
> > [<c104b4cd>] find_task_by_pid_ns+0x6d/0x70
> > [<c104b4e8>] find_task_by_vpid+0x18/0x20
> > [<c1048347>] sys_setpgid+0x47/0x160
> > [<c1002b50>] sysenter_do_call+0x12/0x36
is more helpful messages than messages by WARN_ON() (shown below).
Regards.
----------------------------------------
[PATCH 2.6.35-rc3] Add RCU check for find_task_by_vpid().
find_task_by_vpid() says "Must be called under rcu_read_lock().". But due to
commit 3120438 "rcu: Disable lockdep checking in RCU list-traversal primitives",
we are currently unable to catch "find_task_by_vpid() with tasklist_lock held
but RCU not held" errors.
------------[ cut here ]------------
WARNING: at kernel/pid.c:385 find_task_by_pid_ns+0x5b/0x70()
Hardware name: VMware Virtual Platform
Modules linked in: mptspi mptscsih mptbase scsi_transport_spi
Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1
Call Trace:
[<c104b4bb>] ? find_task_by_pid_ns+0x5b/0x70
[<c103783c>] warn_slowpath_common+0x7c/0xa0
[<c104b4bb>] ? find_task_by_pid_ns+0x5b/0x70
[<c103787d>] warn_slowpath_null+0x1d/0x20
[<c104b4bb>] find_task_by_pid_ns+0x5b/0x70
[<c104b4e8>] find_task_by_vpid+0x18/0x20
[<c1048347>] sys_setpgid+0x47/0x160
[<c1002b50>] sysenter_do_call+0x12/0x36
---[ end trace e68939acb5ea5560 ]---
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
diff --git a/kernel/pid.c b/kernel/pid.c
index e9fd8c1..7123215 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -382,6 +382,7 @@ EXPORT_SYMBOL(pid_task);
*/
struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
{
+ WARN_ON_ONCE(!rcu_read_lock_held());
return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
}
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH 2.6.35-rc3] Add RCU check for find_task_by_vpid().
2010-06-25 22:41 ` Tetsuo Handa
@ 2010-06-28 23:41 ` Paul E. McKenney
0 siblings, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2010-06-28 23:41 UTC (permalink / raw)
To: Tetsuo Handa; +Cc: mingo, linux-kernel
On Sat, Jun 26, 2010 at 07:41:06AM +0900, Tetsuo Handa wrote:
> Hello.
>
> Paul E. McKenney wrote:
> > > diff --git a/kernel/pid.c b/kernel/pid.c
> > > index e9fd8c1..a257471 100644
> > > --- a/kernel/pid.c
> > > +++ b/kernel/pid.c
> > > @@ -382,6 +382,9 @@ EXPORT_SYMBOL(pid_task);
> > > */
> > > struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
> > > {
> > > +#ifdef __do_rcu_dereference_check
> > > + __do_rcu_dereference_check(rcu_read_lock_held());
> > > +#endif
> >
> > How about the following?
> >
> > WARN_ON_ONCE(!rcu_read_lock_held());
> >
> > > return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
> > > }
> > >
> Fine by me if you don't mind WARN_ON_ONCE(!1); for CONFIG_DEBUG_LOCK_ALLOC=n .
> Personally,
>
> > > ===================================================
> > > [ INFO: suspicious rcu_dereference_check() usage. ]
> > > ---------------------------------------------------
> > > kernel/pid.c:386 invoked rcu_dereference_check() without protection!
> > >
> > > other info that might help us debug this:
> > >
> > >
> > > rcu_scheduler_active = 1, debug_locks = 1
> > > 1 lock held by rc.sysinit/1102:
> > > #0: (tasklist_lock){.+.+..}, at: [<c1048340>] sys_setpgid+0x40/0x160
> > >
> > > stack backtrace:
> > > Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1
> > > Call Trace:
> > > [<c105e714>] lockdep_rcu_dereference+0x94/0xb0
> > > [<c104b4cd>] find_task_by_pid_ns+0x6d/0x70
> > > [<c104b4e8>] find_task_by_vpid+0x18/0x20
> > > [<c1048347>] sys_setpgid+0x47/0x160
> > > [<c1002b50>] sysenter_do_call+0x12/0x36
>
> is more helpful messages than messages by WARN_ON() (shown below).
OK, you convinced me. ;-) I will take your earlier patch and remove
the leading "__" from __do_rcu_dereference_check(), and make it be a
first-class RCU API citizen.
Thanx, Paul
> Regards.
> ----------------------------------------
> [PATCH 2.6.35-rc3] Add RCU check for find_task_by_vpid().
>
> find_task_by_vpid() says "Must be called under rcu_read_lock().". But due to
> commit 3120438 "rcu: Disable lockdep checking in RCU list-traversal primitives",
> we are currently unable to catch "find_task_by_vpid() with tasklist_lock held
> but RCU not held" errors.
>
> ------------[ cut here ]------------
> WARNING: at kernel/pid.c:385 find_task_by_pid_ns+0x5b/0x70()
> Hardware name: VMware Virtual Platform
> Modules linked in: mptspi mptscsih mptbase scsi_transport_spi
> Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1
> Call Trace:
> [<c104b4bb>] ? find_task_by_pid_ns+0x5b/0x70
> [<c103783c>] warn_slowpath_common+0x7c/0xa0
> [<c104b4bb>] ? find_task_by_pid_ns+0x5b/0x70
> [<c103787d>] warn_slowpath_null+0x1d/0x20
> [<c104b4bb>] find_task_by_pid_ns+0x5b/0x70
> [<c104b4e8>] find_task_by_vpid+0x18/0x20
> [<c1048347>] sys_setpgid+0x47/0x160
> [<c1002b50>] sysenter_do_call+0x12/0x36
> ---[ end trace e68939acb5ea5560 ]---
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
> diff --git a/kernel/pid.c b/kernel/pid.c
> index e9fd8c1..7123215 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -382,6 +382,7 @@ EXPORT_SYMBOL(pid_task);
> */
> struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
> {
> + WARN_ON_ONCE(!rcu_read_lock_held());
> return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
> }
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2010-06-25 16:08 [PATCH 2.6.35-rc3] Add RCU check for find_task_by_vpid() Tetsuo Handa
2010-06-25 17:48 ` Paul E. McKenney
2010-06-25 22:41 ` Tetsuo Handa
2010-06-28 23:41 ` Paul E. McKenney
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