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author | 2010-06-26 01:08:19 +0900 | |
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committer | 2010-08-19 17:18:02 -0700 | |
commit | 4221a9918e38b7494cee341dda7b7b4bb8c04bde (patch) | |
tree | b79ed7629dd526a9c54dc116b7943cc496b3c19e | |
parent | rcu: simplify the usage of percpu data (diff) | |
download | linux-4221a9918e38b7494cee341dda7b7b4bb8c04bde.tar.gz linux-4221a9918e38b7494cee341dda7b7b4bb8c04bde.tar.bz2 linux-4221a9918e38b7494cee341dda7b7b4bb8c04bde.zip |
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>
-rw-r--r-- | include/linux/rcupdate.h | 14 | ||||
-rw-r--r-- | kernel/pid.c | 1 |
2 files changed, 10 insertions, 5 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index b973dea2d6b0..b124bc6a75ad 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -215,7 +215,11 @@ static inline int rcu_read_lock_sched_held(void) 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 @@ extern int rcu_my_thread_group_empty(void); #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 @@ extern int rcu_my_thread_group_empty(void); #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 @@ extern int rcu_my_thread_group_empty(void); #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 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); } |