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From:   Jia-Ju Bai <baijiaju1990@gmail.com>
To:     bernhard.walle@gmx.de
Cc:     linux-kernel@vger.kernel.org, Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH] firmware: memmap: Replace GFP_ATOMIC with GFP_KERNEL in firmware_map_add_hotplug
Date:   Sat, 27 Jan 2018 00:54:40 +0800
Message-Id: <1516985680-9575-1-git-send-email-baijiaju1990@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

After checking all possible call chains to firmware_map_add_hotplug(),
my tool finds that this function is never called in atomic context,
namely never in an interrupt handler or holding a spinlock.
I manually check the code, and find that
this function is only called by add_memory_resource() that calls 
mem_hotplug_begin(), and mem_hotplug_begin() calls mutex_lock() that
can sleep, so it indicates that firmware_map_add_hotplug()
can call function which can sleep.
Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL.

This is found by a static analysis tool named DCNS written by myself.
And I also manually audit the result.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 drivers/firmware/memmap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/memmap.c b/drivers/firmware/memmap.c
index 5de3ed2..598eb05 100644
--- a/drivers/firmware/memmap.c
+++ b/drivers/firmware/memmap.c
@@ -297,7 +297,7 @@ int __meminit firmware_map_add_hotplug(u64 start, u64 end, const char *type)
 
 	entry = firmware_map_find_entry_bootmem(start, end - 1, type);
 	if (!entry) {
-		entry = kzalloc(sizeof(struct firmware_map_entry), GFP_ATOMIC);
+		entry = kzalloc(sizeof(struct firmware_map_entry), GFP_KERNEL);
 		if (!entry)
 			return -ENOMEM;
 	} else {
-- 
1.7.9.5