From 49f5903b473c5f63f3b57856d1bd4593db0a2eef Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 1 Sep 2015 00:42:57 -0700 Subject: [PATCH] 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 Reviewed-by: Josh Triplett --- 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 bdeb4567b71e..f5f80c5643ac 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 ea95ee1b5ef7..0e93b63bbc59 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 9e6122540d28..a63a1ea5a41b 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); -- 2.30.2