[PATCH 2.6.35-rc3] Add RCU check for find_task_by_vpid().
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From: Tetsuo Handa on 25 Jun 2010 12:10 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 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/ |