Add RCU check for find_task_by_vpid().
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From: Paul E. McKenney on 25 Jun 2010 13:50 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(a)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); > } > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Tetsuo Handa on 25 Jun 2010 18:50 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(a)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); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Paul E. McKenney on 28 Jun 2010 19:50
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(a)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); > } > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |