Commit-ID: 49f5903b473c5f63f3b57856d1bd4593db0a2eef
Gitweb: http://git.kernel.org/tip/49f5903b473c5f63f3b57856d1bd4593db0a2eef
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 1 Sep 2015 00:42:57 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 6 Oct 2015 11:15:43 -0700
rcu: Move preemption disabling out of __srcu_read_lock()
Currently, __srcu_read_lock() cannot be invoked from restricted
environments because it contains calls to preempt_disable() and
preempt_enable(), both of which can invoke lockdep, which is a bad
idea in some restricted execution modes. This commit therefore moves
the preempt_disable() and preempt_enable() from __srcu_read_lock()
to srcu_read_lock(). It also inserts the preempt_disable() and
preempt_enable() around the call to __srcu_read_lock() in do_exit().
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
include/linux/srcu.h | 5 ++++-
kernel/exit.c | 2 ++
kernel/rcu/srcu.c | 2 --
3 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index bdeb456..f5f80c5 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -215,8 +215,11 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp)
*/
static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
{
- int retval = __srcu_read_lock(sp);
+ int retval;
+ preempt_disable();
+ retval = __srcu_read_lock(sp);
+ preempt_enable();
rcu_lock_acquire(&(sp)->dep_map);
return retval;
}
diff --git a/kernel/exit.c b/kernel/exit.c
index ea95ee1..0e93b63 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -761,7 +761,9 @@ void do_exit(long code)
*/
flush_ptrace_hw_breakpoint(tsk);
+ TASKS_RCU(preempt_disable());
TASKS_RCU(tasks_rcu_i = __srcu_read_lock(&tasks_rcu_exit_srcu));
+ TASKS_RCU(preempt_enable());
exit_notify(tsk, group_dead);
proc_exit_connector(tsk);
#ifdef CONFIG_NUMA
diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index 9e61225..a63a1ea 100644
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -298,11 +298,9 @@ int __srcu_read_lock(struct srcu_struct *sp)
int idx;
idx = READ_ONCE(sp->completed) & 0x1;
- preempt_disable();
__this_cpu_inc(sp->per_cpu_ref->c[idx]);
smp_mb(); /* B */ /* Avoid leaking the critical section. */
__this_cpu_inc(sp->per_cpu_ref->seq[idx]);
- preempt_enable();
return idx;
}
EXPORT_SYMBOL_GPL(__srcu_read_lock);
--
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