linux-kernel - [PATCH 1/7] proc/kcore: don't grab lock for kclist

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Message-Id: <a02eecc5a0ab14e5a65407472f827abfc6554e03.1530904769.git.osandov@fb.com>
Date:   Fri,  6 Jul 2018 12:32:32 -0700
From:   Omar Sandoval <osandov@...ndov.com>
To:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Alexey Dobriyan <adobriyan@...il.com>
Cc:     Eric Biederman <ebiederm@...ssion.com>, kernel-team@...com
Subject: [PATCH 1/7] proc/kcore: don't grab lock for kclist_add()

From: Omar Sandoval <osandov@...com>

kclist_add() is only called at init time, so there's no point in
grabbing any locks. We're also going to replace the rwlock with a rwsem,
which we don't want to try grabbing during early boot.

Signed-off-by: Omar Sandoval <osandov@...com>
---
 fs/proc/kcore.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index e64ecb9f2720..afd1ff8c2d3f 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -62,6 +62,7 @@ static LIST_HEAD(kclist_head);
 static DEFINE_RWLOCK(kclist_lock);
 static int kcore_need_update = 1;
 
+/* This doesn't grab kclist_lock, so it should only be used at init time. */
 void
 kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
 {
@@ -69,9 +70,7 @@ kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
 	new->size = size;
 	new->type = type;
 
-	write_lock(&kclist_lock);
 	list_add_tail(&new->list, &kclist_head);
-	write_unlock(&kclist_lock);
 }
 
 static size_t get_kcore_size(int *nphdr, size_t *elf_buflen)
-- 
2.18.0