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 v3 2/8] proc/kcore: don't grab lock for memory hotplug notifier
Date: Wed, 18 Jul 2018 15:58:42 -0700 [thread overview]
Message-ID: <0a4bc89f4dbde8b5b2ea309f7b4fb6a85fe29df2.1531953780.git.osandov@fb.com> (raw)
In-Reply-To: <cover.1531953780.git.osandov@fb.com>
From: Omar Sandoval <osandov@fb.com>
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.
Signed-off-by: Omar Sandoval <osandov@fb.com>
---
fs/proc/kcore.c | 6 ++----
1 file 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;
}
--
2.18.0
next prev parent reply other threads:[~2018-07-18 23:39 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-18 22:58 [PATCH v3 0/8] /proc/kcore improvements Omar Sandoval
2018-07-18 22:58 ` [PATCH v3 1/8] proc/kcore: don't grab lock for kclist_add() Omar Sandoval
2018-07-18 22:58 ` Omar Sandoval [this message]
2018-07-18 22:58 ` [PATCH v3 3/8] proc/kcore: replace kclist_lock rwlock with rwsem Omar Sandoval
2018-07-18 22:58 ` [PATCH v3 4/8] proc/kcore: fix memory hotplug vs multiple opens race Omar Sandoval
2018-07-18 22:58 ` [PATCH v3 5/8] proc/kcore: hold lock during read Omar Sandoval
2018-07-24 15:11 ` Tetsuo Handa
2018-07-25 23:34 ` Omar Sandoval
2018-07-18 22:58 ` [PATCH v3 6/8] proc/kcore: clean up ELF header generation Omar Sandoval
2018-07-18 22:58 ` [PATCH v3 7/8] proc/kcore: optimize multiple page reads Omar Sandoval
2018-08-28 10:59 ` KASAN error in " Dominique Martinet
2018-08-29 4:04 ` [PATCH] proc/kcore: fix invalid memory access in multi-page read optimization Dominique Martinet
2018-09-04 18:03 ` Omar Sandoval
2018-09-04 22:24 ` Dominique Martinet
2018-09-04 22:35 ` [PATCH v2] " Dominique Martinet
2018-09-04 22:38 ` [PATCH v3] " Dominique Martinet
2018-09-04 22:41 ` Omar Sandoval
2018-09-05 19:56 ` Bhupesh Sharma
2018-09-05 20:57 ` Andrew Morton
2018-09-05 22:00 ` Dominique Martinet
2018-07-18 22:58 ` [PATCH v3 8/8] proc/kcore: add vmcoreinfo note to /proc/kcore Omar Sandoval
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