Commit db1466b3 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

rcu: Use wrapper function instead of exporting tasklist_lock 



Lockdep-RCU commit d11c563d exported tasklist_lock, which is not
a good thing.  This patch instead exports a function that uses
lockdep to check whether tasklist_lock is held.

Suggested-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: Christoph Hellwig <hch@lst.de>
LKML-Reference: <1267631219-8713-1-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 0e064caf

include/linux/cred.h

+1 −1
Original line number Diff line number Diff line
@@ -280,7 +280,7 @@ static inline void put_cred(const struct cred *_cred) 
 * task or by holding tasklist_lock to prevent it from being unlinked.

 */

#define __task_cred(task) \

	((const struct cred *)(rcu_dereference_check((task)->real_cred, rcu_read_lock_held() || lockdep_is_held(&tasklist_lock))))

	((const struct cred *)(rcu_dereference_check((task)->real_cred, rcu_read_lock_held() || lockdep_tasklist_lock_is_held())))



/**

 * get_task_cred - Get another task's objective credentials

include/linux/sched.h

+4 −0
Original line number Diff line number Diff line
@@ -258,6 +258,10 @@ extern spinlock_t mmlist_lock; 


struct task_struct;



#ifdef CONFIG_PROVE_RCU

extern int lockdep_tasklist_lock_is_held(void);

#endif /* #ifdef CONFIG_PROVE_RCU */



extern void sched_init(void);

extern void sched_init_smp(void);

extern asmlinkage void schedule_tail(struct task_struct *prev);

kernel/exit.c

+1 −1
Original line number Diff line number Diff line
@@ -87,7 +87,7 @@ static void __exit_signal(struct task_struct *tsk) 


	sighand = rcu_dereference_check(tsk->sighand,

					rcu_read_lock_held() ||

					lockdep_is_held(&tasklist_lock));

					lockdep_tasklist_lock_is_held());

	spin_lock(&sighand->siglock);



	posix_cpu_timers_exit(tsk);

kernel/fork.c

+8 −1
Original line number Diff line number Diff line
@@ -86,7 +86,14 @@ int max_threads; /* tunable limit on nr_threads */ 
DEFINE_PER_CPU(unsigned long, process_counts) = 0;



__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */

EXPORT_SYMBOL_GPL(tasklist_lock);



#ifdef CONFIG_PROVE_RCU

int lockdep_tasklist_lock_is_held(void)

{

	return lockdep_is_held(&tasklist_lock);

}

EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);

#endif /* #ifdef CONFIG_PROVE_RCU */



int nr_processes(void)

{

kernel/pid.c

+3 −1
Original line number Diff line number Diff line
@@ -367,7 +367,9 @@ struct task_struct *pid_task(struct pid *pid, enum pid_type type) 
	struct task_struct *result = NULL;

	if (pid) {

		struct hlist_node *first;

		first = rcu_dereference_check(pid->tasks[type].first, rcu_read_lock_held() || lockdep_is_held(&tasklist_lock));

		first = rcu_dereference_check(pid->tasks[type].first,

					      rcu_read_lock_held() ||

					      lockdep_tasklist_lock_is_held());

		if (first)

			result = hlist_entry(first, struct task_struct, pids[(type)].node);

	}

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