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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2018-04-25 13:01:25 -0700
committerPaul E. McKenney <paulmck@linux.ibm.com>2018-11-08 21:54:14 -0800
commit0607ba8403c4cdb253f8c5200ecf654dfb7790cc (patch)
tree1c980c7df600c90717f87172df7d9259a233a87a /kernel/rcu/srcutree.c
parentf3e763c3e544b73ae5c4a3842cedb9ff6ca37715 (diff)
srcu: Prevent __call_srcu() counter wrap with read-side critical section
Ever since cdf7abc4610a ("srcu: Allow use of Tiny/Tree SRCU from both process and interrupt context"), it has been permissible to use SRCU read-side critical sections in interrupt context. This allows __call_srcu() to use SRCU read-side critical sections to prevent a new SRCU grace period from ending before the call to either srcu_funnel_gp_start() or srcu_funnel_exp_start completes, thus preventing SRCU grace-period counter overflow during that time. Note that this does not permit removal of the counter-wrap checks in srcu_gp_end(). These check are necessary to handle the case where a given CPU does not interact at all with SRCU for an extended time period. This commit therefore adds an SRCU read-side critical section to __call_srcu() in order to prevent grace period counter wrap during the funnel-locking process. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/srcutree.c')
-rw-r--r--kernel/rcu/srcutree.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index a8846ed7f352..60f3236beaf7 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -858,6 +858,7 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp,
rcu_callback_t func, bool do_norm)
{
unsigned long flags;
+ int idx;
bool needexp = false;
bool needgp = false;
unsigned long s;
@@ -871,6 +872,7 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp,
return;
}
rhp->func = func;
+ idx = srcu_read_lock(sp);
local_irq_save(flags);
sdp = this_cpu_ptr(sp->sda);
spin_lock_rcu_node(sdp);
@@ -892,6 +894,7 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp,
srcu_funnel_gp_start(sp, sdp, s, do_norm);
else if (needexp)
srcu_funnel_exp_start(sp, sdp->mynode, s);
+ srcu_read_unlock(sp, idx);
}
/**