From c927dddeac30d11dedfdfa416dd4a8051fa286b0 Mon Sep 17 00:00:00 2001
Message-Id: <c927dddeac30d11dedfdfa416dd4a8051fa286b0.1594742966.git.zanussi@kernel.org>
In-Reply-To: <832f7d97d6b989a5b4860dd2dbec58ad6ad5ab81.1594742966.git.zanussi@kernel.org>
References: <832f7d97d6b989a5b4860dd2dbec58ad6ad5ab81.1594742966.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 12 Oct 2017 18:37:12 +0200
Subject: [PATCH 162/329] srcu: replace local_irqsave() with a locallock
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.132-rt59.tar.xz

There are two instances which disable interrupts in order to become a
stable this_cpu_ptr() pointer. The restore part is coupled with
spin_unlock_irqrestore() which does not work on RT.
Replace the local_irq_save() call with the appropriate local_lock()
version of it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/rcu/srcutree.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index df0375453ba1..0f09a1a9e17c 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -39,6 +39,7 @@
 #include <linux/module.h>
 #include <linux/srcu.h>
 #include <linux/cpu.h>
+#include <linux/locallock.h>
 
 #include "rcu.h"
 #include "rcu_segcblist.h"
@@ -760,6 +761,8 @@ static void srcu_flip(struct srcu_struct *sp)
  * negligible when amoritized over that time period, and the extra latency
  * of a needlessly non-expedited grace period is similarly negligible.
  */
+static DEFINE_LOCAL_IRQ_LOCK(sp_llock);
+
 static bool srcu_might_be_idle(struct srcu_struct *sp)
 {
 	unsigned long curseq;
@@ -768,13 +771,13 @@ static bool srcu_might_be_idle(struct srcu_struct *sp)
 	unsigned long t;
 
 	/* If the local srcu_data structure has callbacks, not idle.  */
-	local_irq_save(flags);
+	local_lock_irqsave(sp_llock, flags);
 	sdp = this_cpu_ptr(sp->sda);
 	if (rcu_segcblist_pend_cbs(&sdp->srcu_cblist)) {
-		local_irq_restore(flags);
+		local_unlock_irqrestore(sp_llock, flags);
 		return false; /* Callbacks already present, so not idle. */
 	}
-	local_irq_restore(flags);
+	local_unlock_irqrestore(sp_llock, flags);
 
 	/*
 	 * No local callbacks, so probabalistically probe global state.
@@ -852,7 +855,7 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp,
 		return;
 	}
 	rhp->func = func;
-	local_irq_save(flags);
+	local_lock_irqsave(sp_llock, flags);
 	sdp = this_cpu_ptr(sp->sda);
 	spin_lock_rcu_node(sdp);
 	rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp, false);
@@ -868,7 +871,8 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp,
 		sdp->srcu_gp_seq_needed_exp = s;
 		needexp = true;
 	}
-	spin_unlock_irqrestore_rcu_node(sdp, flags);
+	spin_unlock_rcu_node(sdp);
+	local_unlock_irqrestore(sp_llock, flags);
 	if (needgp)
 		srcu_funnel_gp_start(sp, sdp, s, do_norm);
 	else if (needexp)
-- 
2.17.1

