[PATCH v2 1/7] proc/kcore: don't grab lock for kclist_add()

From: Omar Sandoval <osandov@osandov.com>
To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
	Eric Biederman <ebiederm@xmission.com>,
	James Morse <james.morse@arm.com>,
	Bhupesh Sharma <bhsharma@redhat.com>,
	kernel-team@fb.com
Subject: [PATCH v2 1/7] proc/kcore: don't grab lock for kclist_add()
Date: Thu, 12 Jul 2018 17:09:33 -0700	[thread overview]
Message-ID: <ddbe991f42b8d49e50645878ad8c1a8168db2e82.1531440458.git.osandov@fb.com> (raw)
In-Reply-To: <cover.1531440458.git.osandov@fb.com>

From: Omar Sandoval <osandov@fb.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@fb.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 66c373230e60..ddeeb3a5a015 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

