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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-03-03 07:46:56 -0800
committerIngo Molnar <mingo@elte.hu>2010-03-04 11:46:14 +0100
commitdb1466b3e1bd1727375cdbfcbea4bcce2f860f61 (patch)
treee56e8d7b82f8851e570d95f531ec62e4d107967a
parent0e064caf6402d1d67db4233d26beec88ca212919 (diff)
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>
-rw-r--r--include/linux/cred.h2
-rw-r--r--include/linux/sched.h4
-rw-r--r--kernel/exit.c2
-rw-r--r--kernel/fork.c9
-rw-r--r--kernel/pid.c4
5 files changed, 17 insertions, 4 deletions
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 4db09f89b637..52507c3e1387 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -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
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0eef87b58ea5..a47af2064dcc 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -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);
diff --git a/kernel/exit.c b/kernel/exit.c
index 45ed043b8bf5..fed3a4db6f04 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -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);
diff --git a/kernel/fork.c b/kernel/fork.c
index 17bbf093356d..8691c540a470 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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)
{
diff --git a/kernel/pid.c b/kernel/pid.c
index b08e697cd83f..b6064405f367 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -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);
}