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authorOmar Sandoval <osandov@fb.com>2018-08-22 07:54:55 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-22 20:52:46 +0300
commitbf53183164dbba00b342df7d2215b33007ed83ed (patch)
tree679d8cf52528ddbcffbbf773703fae7fa3225a61 /fs/proc
parenta8dd9c4df18edc873d244790d163564a5d17626b (diff)
downloadlinux-bf53183164dbba00b342df7d2215b33007ed83ed.tar.xz
proc/kcore: don't grab lock for memory hotplug notifier
The memory hotplug notifier kcore_callback() only needs kclist_lock to prevent races with __kcore_update_ram(), but we can easily eliminate that race by using an atomic xchg() in __kcore_update_ram(). This is preparation for converting kclist_lock to an rwsem. Link: http://lkml.kernel.org/r/0a4bc89f4dbde8b5b2ea309f7b4fb6a85fe29df2.1531953780.git.osandov@fb.com Signed-off-by: Omar Sandoval <osandov@fb.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Bhupesh Sharma <bhsharma@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: James Morse <james.morse@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/kcore.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index b0b9a76f28d6..e83f15a4f66d 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -118,7 +118,7 @@ static void __kcore_update_ram(struct list_head *list)
LIST_HEAD(garbage);
write_lock(&kclist_lock);
- if (kcore_need_update) {
+ if (xchg(&kcore_need_update, 0)) {
list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
if (pos->type == KCORE_RAM
|| pos->type == KCORE_VMEMMAP)
@@ -127,7 +127,6 @@ static void __kcore_update_ram(struct list_head *list)
list_splice_tail(list, &kclist_head);
} else
list_splice(list, &garbage);
- kcore_need_update = 0;
proc_root_kcore->size = get_kcore_size(&nphdr, &size);
write_unlock(&kclist_lock);
@@ -593,9 +592,8 @@ static int __meminit kcore_callback(struct notifier_block *self,
switch (action) {
case MEM_ONLINE:
case MEM_OFFLINE:
- write_lock(&kclist_lock);
kcore_need_update = 1;
- write_unlock(&kclist_lock);
+ break;
}
return NOTIFY_OK;
}