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: [<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
Commit updated to use a new rcu_lockdep_assert() exported API rather than
the old internal __do_rcu_dereference().
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index b973dea..b124bc6 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -215,7 +215,11 @@
extern int rcu_my_thread_group_empty(void);
-#define __do_rcu_dereference_check(c) \
+/**
+ * rcu_lockdep_assert - emit lockdep splat if specified condition not met
+ * @c: condition to check
+ */
+#define rcu_lockdep_assert(c) \
do { \
static bool __warned; \
if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \
@@ -226,7 +230,7 @@
#else /* #ifdef CONFIG_PROVE_RCU */
-#define __do_rcu_dereference_check(c) do { } while (0)
+#define rcu_lockdep_assert(c) do { } while (0)
#endif /* #else #ifdef CONFIG_PROVE_RCU */
@@ -247,14 +251,14 @@
#define __rcu_dereference_check(p, c, space) \
({ \
typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \
- __do_rcu_dereference_check(c); \
+ rcu_lockdep_assert(c); \
(void) (((typeof (*p) space *)p) == p); \
smp_read_barrier_depends(); \
((typeof(*p) __force __kernel *)(_________p1)); \
})
#define __rcu_dereference_protected(p, c, space) \
({ \
- __do_rcu_dereference_check(c); \
+ rcu_lockdep_assert(c); \
(void) (((typeof (*p) space *)p) == p); \
((typeof(*p) __force __kernel *)(p)); \
})
@@ -262,7 +266,7 @@
#define __rcu_dereference_index_check(p, c) \
({ \
typeof(p) _________p1 = ACCESS_ONCE(p); \
- __do_rcu_dereference_check(c); \
+ rcu_lockdep_assert(c); \
smp_read_barrier_depends(); \
(_________p1); \
})
diff --git a/kernel/pid.c b/kernel/pid.c
index 0f90c2f..39b65b6 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -416,6 +416,7 @@
*/
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);
}