linux-kernel - [GIT PULL] RCU fixes

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Date:   Sat, 10 Jun 2017 10:43:45 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...ibm.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] RCU fixes

Linus,

Please pull the latest rcu-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git rcu-urgent-for-linus

   # HEAD: 8affb06737ae565722764c2b309eb0e892538344 Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into rcu/urgent

Fix an SRCU bug affecting KVM IRQ injection.

 Thanks,

	Ingo

------------------>
Paolo Bonzini (2):
      srcu: Allow use of Tiny/Tree SRCU from both process and interrupt context
      srcu: Allow use of Classic SRCU from both process and interrupt context


 include/linux/srcu.h  | 2 --
 kernel/rcu/srcu.c     | 5 ++---
 kernel/rcu/srcutiny.c | 7 ++++---
 kernel/rcu/srcutree.c | 5 ++---
 4 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 167ad8831aaf..4c1d5f7e62c4 100644
--- 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
index 584d8a983883..dea03614263f 100644
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -263,7 +263,7 @@ 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)
@@ -271,7 +271,7 @@ 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
index 36e1f82faed1..32798eb14853 100644
--- 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
index 3ae8474557df..157654fa436a 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -357,7 +357,7 @@ 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)
@@ -365,7 +365,7 @@ 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)
 {