Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kerne…

…l/git/paulmck/linux-rcu into rcu/urgent Pull RCU fix from Paul E. McKenney: " This series enables srcu_read_lock() and srcu_read_unlock() to be used from interrupt handlers, which fixes a bug in KVM's use of SRCU in delivery of interrupts to guest OSes. " Signed-off-by: Ingo Molnar <[email protected]>
akvadrako · Jun 9, 2017 · 8affb06 · 8affb06
2 parents b29794e + 1123a60
commit 8affb06
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Showing 4 changed files with 8 additions and 11 deletions.
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
@@ -172,9 +172,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
 {
 	int retval;
 
-	preempt_disable();
 	retval = __srcu_read_lock(sp);
-	preempt_enable();
 	rcu_lock_acquire(&(sp)->dep_map);
 	return retval;
 }

diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
@@ -263,15 +263,15 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
 /*
  * Counts the new reader in the appropriate per-CPU element of the
- * srcu_struct.  Must be called from process context.
+ * srcu_struct.
  * Returns an index that must be passed to the matching srcu_read_unlock().
  */
 int __srcu_read_lock(struct srcu_struct *sp)
 {
 	int idx;
 
 	idx = READ_ONCE(sp->completed) & 0x1;
-	__this_cpu_inc(sp->per_cpu_ref->lock_count[idx]);
+	this_cpu_inc(sp->per_cpu_ref->lock_count[idx]);
 	smp_mb(); /* B */  /* Avoid leaking the critical section. */
 	return idx;
 }
@@ -281,7 +281,6 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
  * Removes the count for the old reader from the appropriate per-CPU
  * element of the srcu_struct.  Note that this may well be a different
  * CPU than that which was incremented by the corresponding srcu_read_lock().
- * Must be called from process context.
  */
 void __srcu_read_unlock(struct srcu_struct *sp, int idx)
 {

diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
@@ -97,8 +97,9 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
 /*
  * Counts the new reader in the appropriate per-CPU element of the
- * srcu_struct.  Must be called from process context.
- * Returns an index that must be passed to the matching srcu_read_unlock().
+ * srcu_struct.  Can be invoked from irq/bh handlers, but the matching
+ * __srcu_read_unlock() must be in the same handler instance.  Returns an
+ * index that must be passed to the matching srcu_read_unlock().
  */
 int __srcu_read_lock(struct srcu_struct *sp)
 {
@@ -112,7 +113,7 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
 
 /*
  * Removes the count for the old reader from the appropriate element of
- * the srcu_struct.  Must be called from process context.
+ * the srcu_struct.
  */
 void __srcu_read_unlock(struct srcu_struct *sp, int idx)
 {

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
@@ -357,15 +357,15 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
 /*
  * Counts the new reader in the appropriate per-CPU element of the
- * srcu_struct.  Must be called from process context.
+ * srcu_struct.
  * Returns an index that must be passed to the matching srcu_read_unlock().
  */
 int __srcu_read_lock(struct srcu_struct *sp)
 {
 	int idx;
 
 	idx = READ_ONCE(sp->srcu_idx) & 0x1;
-	__this_cpu_inc(sp->sda->srcu_lock_count[idx]);
+	this_cpu_inc(sp->sda->srcu_lock_count[idx]);
 	smp_mb(); /* B */  /* Avoid leaking the critical section. */
 	return idx;
 }
@@ -375,7 +375,6 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
  * Removes the count for the old reader from the appropriate per-CPU
  * element of the srcu_struct.  Note that this may well be a different
  * CPU than that which was incremented by the corresponding srcu_read_lock().
- * Must be called from process context.
  */
 void __srcu_read_unlock(struct srcu_struct *sp, int idx)
 {