From 9d829d94da0a654cb00678e64c3ef938ad6163ec Mon Sep 17 00:00:00 2001
Message-Id: <9d829d94da0a654cb00678e64c3ef938ad6163ec.1599166690.git.zanussi@kernel.org>
In-Reply-To: <56457dc415803c8abc5acb513ada877a79596f05.1599166690.git.zanussi@kernel.org>
References: <56457dc415803c8abc5acb513ada877a79596f05.1599166690.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 31 Aug 2018 14:16:30 +0200
Subject: [PATCH 021/333] of: allocate / free phandle cache outside of the
 devtree_lock
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.142-rt63.tar.xz

The phandle cache code allocates memory while holding devtree_lock which
is a raw_spinlock_t. Memory allocation (and free()) is not possible on
RT while a raw_spinlock_t is held.
Invoke the kfree() and kcalloc() while the lock is dropped.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/of/base.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index f0dbb7ad88cf..c59b30bab0e0 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -130,31 +130,34 @@ static u32 phandle_cache_mask;
 /*
  * Caller must hold devtree_lock.
  */
-static void __of_free_phandle_cache(void)
+static struct device_node** __of_free_phandle_cache(void)
 {
 	u32 cache_entries = phandle_cache_mask + 1;
 	u32 k;
+	struct device_node **shadow;
 
 	if (!phandle_cache)
-		return;
+		return NULL;
 
 	for (k = 0; k < cache_entries; k++)
 		of_node_put(phandle_cache[k]);
 
-	kfree(phandle_cache);
+	shadow = phandle_cache;
 	phandle_cache = NULL;
+	return shadow;
 }
 
 int of_free_phandle_cache(void)
 {
 	unsigned long flags;
+	struct device_node **shadow;
 
 	raw_spin_lock_irqsave(&devtree_lock, flags);
 
-	__of_free_phandle_cache();
+	shadow = __of_free_phandle_cache();
 
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
-
+	kfree(shadow);
 	return 0;
 }
 #if !defined(CONFIG_MODULES)
@@ -189,10 +192,11 @@ void of_populate_phandle_cache(void)
 	u32 cache_entries;
 	struct device_node *np;
 	u32 phandles = 0;
+	struct device_node **shadow;
 
 	raw_spin_lock_irqsave(&devtree_lock, flags);
 
-	__of_free_phandle_cache();
+	shadow = __of_free_phandle_cache();
 
 	for_each_of_allnodes(np)
 		if (np->phandle && np->phandle != OF_PHANDLE_ILLEGAL)
@@ -200,12 +204,14 @@ void of_populate_phandle_cache(void)
 
 	if (!phandles)
 		goto out;
+	raw_spin_unlock_irqrestore(&devtree_lock, flags);
 
 	cache_entries = roundup_pow_of_two(phandles);
 	phandle_cache_mask = cache_entries - 1;
 
 	phandle_cache = kcalloc(cache_entries, sizeof(*phandle_cache),
 				GFP_ATOMIC);
+	raw_spin_lock_irqsave(&devtree_lock, flags);
 	if (!phandle_cache)
 		goto out;
 
@@ -217,6 +223,7 @@ void of_populate_phandle_cache(void)
 
 out:
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
+	kfree(shadow);
 }
 
 void __init of_core_init(void)
-- 
2.17.1

