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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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Paul 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: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul E. McKenney 2010-03-03 07:46:56 -08:00 committed by Ingo Molnar
parent 0e064caf64
commit db1466b3e1
5 changed files with 17 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/cred.h
View File

@ -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

4
include/linux/sched.h
View File

@ -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);

2
kernel/exit.c
View File

@ -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);

9
kernel/fork.c
View File

@ -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)
{

4
kernel/pid.c
View File

@ -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);
}