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rcu: Move preemption disabling out of __srcu_read_lock()

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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@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney 2015-09-01 00:42:57 -07:00
parent 7f21aeef72
commit 49f5903b47
3 changed files with 6 additions and 3 deletions
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5
include/linux/srcu.h
View File

@ -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;
}

2
kernel/exit.c
View File

@ -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

2
kernel/rcu/srcu.c
View File

@ -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);