The patch titled
Subject: epoll-use-refcount-to-reduce-ep_mutex-contention-v5
has been added to the -mm mm-nonmm-unstable branch. Its filename is
epoll-use-refcount-to-reduce-ep_mutex-contention-v5.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/epoll-use-refcount-to-reduce-ep_mutex-contention-v5.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Paolo Abeni <pabeni@xxxxxxxxxx>
Subject: epoll-use-refcount-to-reduce-ep_mutex-contention-v5
Date: Wed, 8 Mar 2023 22:51:31 +0100
update some comments
Link: https://lkml.kernel.org/r/323de732635cc3513c1837c6cbb98f012174f994.1678312201.git.pabeni@xxxxxxxxxx
Tested-by: Xiumei Mu <xmu@xxxxxxxxxxx>
Reviewed-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>
Acked-by: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/fs/eventpoll.c~epoll-use-refcount-to-reduce-ep_mutex-contention-v5
+++ a/fs/eventpoll.c
@@ -714,6 +714,8 @@ static void ep_free(struct eventpoll *ep
* Removes a "struct epitem" from the eventpoll RB tree and deallocates
* all the associated resources. Must be called with "mtx" held.
* If the dying flag is set, do the removal only if force is true.
+ * This prevents ep_clear_and_put() from dropping all the ep references
+ * while running concurrently with eventpoll_release_file().
* Returns true if the eventpoll can be disposed.
*/
static bool __ep_remove(struct eventpoll *ep, struct epitem *epi, bool force)
@@ -941,14 +943,13 @@ void eventpoll_release_file(struct file
bool dispose;
/*
- * Use the 'dying' flag to prevent a concurrent ep_cleat_and_put() from
+ * Use the 'dying' flag to prevent a concurrent ep_clear_and_put() from
* touching the epitems list before eventpoll_release_file() can access
* the ep->mtx.
*/
again:
spin_lock(&file->f_lock);
if (file->f_ep && file->f_ep->first) {
- /* detach from ep tree */
epi = hlist_entry(file->f_ep->first, struct epitem, fllink);
epi->dying = true;
spin_unlock(&file->f_lock);
_
Patches currently in -mm which might be from pabeni@xxxxxxxxxx are
epoll-use-refcount-to-reduce-ep_mutex-contention.patch
epoll-use-refcount-to-reduce-ep_mutex-contention-v5.patch
