diff options
| 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 | |
| parent | rcu: Use IS_ENABLED() to CONFIG_RCU_FANOUT_EXACT #ifdef (diff) | |
| download | linux-dev-d24209bb689e2c7f7418faec9b4a948e922d24da.tar.xz linux-dev-d24209bb689e2c7f7418faec9b4a948e922d24da.zip | |
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>
| -rw-r--r-- | include/linux/lockdep.h | 7 | ||||
| -rw-r--r-- | include/linux/rcupdate.h | 2 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 8 |
3 files changed, 14 insertions, 3 deletions
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 74ab23176e9b..066ba4157541 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -531,8 +531,13 @@ do { \ # define might_lock_read(lock) do { } while (0) #endif -#ifdef CONFIG_PROVE_RCU +#ifdef CONFIG_LOCKDEP void lockdep_rcu_suspicious(const char *file, const int line, const char *s); +#else +static inline void +lockdep_rcu_suspicious(const char *file, const int line, const char *s) +{ +} #endif #endif /* __LINUX_LOCKDEP_H */ diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 3e6afed51051..70b896e16f19 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -942,9 +942,9 @@ static inline void rcu_read_unlock(void) { rcu_lockdep_assert(rcu_is_watching(), "rcu_read_unlock() used illegally while idle"); - rcu_lock_release(&rcu_lock_map); __release(RCU); __rcu_read_unlock(); + rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ } /** 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; } |