From 67bdbffd696f29a0b68aa8daa285783a06651583 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 25 Feb 2010 16:55:13 +0100 Subject: rculist: avoid __rcu annotations This avoids warnings from missing __rcu annotations in the rculist implementation, making it possible to use the same lists in both RCU and non-RCU cases. We can add rculist annotations later, together with lockdep support for rculist, which is missing as well, but that may involve changing all the users. Signed-off-by: Arnd Bergmann Signed-off-by: Paul E. McKenney Cc: Pavel Emelyanov Cc: Sukadev Bhattiprolu Reviewed-by: Josh Triplett --- kernel/pid.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/pid.c') diff --git a/kernel/pid.c b/kernel/pid.c index d55c6fb8d087..0f90c2f713f1 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -401,7 +401,7 @@ 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, + first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]), rcu_read_lock_held() || lockdep_tasklist_lock_is_held()); if (first) -- cgit v1.2.3 From 4221a9918e38b7494cee341dda7b7b4bb8c04bde Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Sat, 26 Jun 2010 01:08:19 +0900 Subject: 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 lock not held" errors due to the RCU-lockdep checks being suppressed in the RCU variants of the struct list_head traversals. This commit therefore places an explicit check for being in an RCU read-side critical section in find_task_by_pid_ns(). =================================================== [ 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: [] sys_setpgid+0x40/0x160 stack backtrace: Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1 Call Trace: [] lockdep_rcu_dereference+0x94/0xb0 [] find_task_by_pid_ns+0x6d/0x70 [] find_task_by_vpid+0x18/0x20 [] sys_setpgid+0x47/0x160 [] sysenter_do_call+0x12/0x36 Commit updated to use a new rcu_lockdep_assert() exported API rather than the old internal __do_rcu_dereference(). Signed-off-by: Tetsuo Handa Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/pid.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/pid.c') diff --git a/kernel/pid.c b/kernel/pid.c index 0f90c2f713f1..39b65b69584f 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -416,6 +416,7 @@ EXPORT_SYMBOL(pid_task); */ struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns) { + rcu_lockdep_assert(rcu_read_lock_held()); return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID); } -- cgit v1.2.3