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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-01-21 15:26:03 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-03-03 11:16:00 -0800 |
| commit | d24209bb689e2c7f7418faec9b4a948e922d24da (patch) | |
| tree | 40db37902a30acb68f5733e666f25ea7b52e8485 /kernel/rcu | |
| parent | 6629240575992a6f0d18c46f5160b34527b0e501 (diff) | |
| download | linux-d24209bb689e2c7f7418faec9b4a948e922d24da.tar.bz2 | |
rcu: Improve diagnostics for blocked critical sections in irq
If an RCU read-side critical section occurs within an interrupt handler
or a softirq handler, it cannot have been preempted. Therefore, there is
a check in rcu_read_unlock_special() checking for this error. However,
when this check triggers, it lacks diagnostic information. This commit
therefore moves rcu_read_unlock()'s lockdep annotation to follow the
call to __rcu_read_unlock() and changes rcu_read_unlock_special()'s
WARN_ON_ONCE() to an lockdep_rcu_suspicious() in order to locate where
the offending RCU read-side critical section began. In addition, the
value of the ->rcu_read_unlock_special field is printed.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 0a571e9a0f1d..8a33920b8845 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -334,7 +334,13 @@ void rcu_read_unlock_special(struct task_struct *t) } /* Hardware IRQ handlers cannot block, complain if they get here. */ - if (WARN_ON_ONCE(in_irq() || in_serving_softirq())) { + if (in_irq() || in_serving_softirq()) { + lockdep_rcu_suspicious(__FILE__, __LINE__, + "rcu_read_unlock() from irq or softirq with blocking in critical section!!!\n"); + pr_alert("->rcu_read_unlock_special: %#x (b: %d, nq: %d)\n", + t->rcu_read_unlock_special.s, + t->rcu_read_unlock_special.b.blocked, + t->rcu_read_unlock_special.b.need_qs); local_irq_restore(flags); return; } |