From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C4C6C433F5 for ; Thu, 9 Dec 2021 01:06:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241816AbhLIBKI (ORCPT ); Wed, 8 Dec 2021 20:10:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241723AbhLIBKE (ORCPT ); Wed, 8 Dec 2021 20:10:04 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84814C061746; Wed, 8 Dec 2021 17:06:31 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 0E284B8235B; Thu, 9 Dec 2021 01:06:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81510C341CA; Thu, 9 Dec 2021 01:06:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1639011988; bh=JSyZz0sb7RhFw3Zf+ynfEZJrO9JuZhu8RB5wW2VzICE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IYfFZYF9PWn4E0itq5qzHz2Fkzp2T0qSCiTnG4jxoWJGE9dC1KOjuFwAPx9ndZNkD a2+Wh4DKFqBqSQxDGYnBDiIohvgBbpCJW7HtlCwtU1JNdwB44wZOsf69MDxzY1AXPZ U+2aQ4ThGx6no4X9m9faRTlACCs2BVx+bSNgyvdzKr/FZfoVRJ219iWKuAMiD1GOdB w3DQSPzE9s5QHtI5U0hccgYiQcCwng4uLAS9R31zsiHRr1ztcmnl54iB8I2+vJHszh /hxTrKj8v7yMDqkO+IaVBBam+qivLRiCa5wyoIkKxysjllcfAhRN5Y4VHelKReSoFy GLGiV6uYXj5MA== From: Eric Biggers To: Alexander Viro , Benjamin LaHaise Cc: linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Ramji Jiyani , Christoph Hellwig , Linus Torvalds , Oleg Nesterov , Jens Axboe , Martijn Coenen , stable@vger.kernel.org Subject: [PATCH v3 2/5] binder: use wake_up_pollfree() Date: Wed, 8 Dec 2021 17:04:52 -0800 Message-Id: <20211209010455.42744-3-ebiggers@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211209010455.42744-1-ebiggers@kernel.org> References: <20211209010455.42744-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Biggers wake_up_poll() uses nr_exclusive=1, so it's not guaranteed to wake up all exclusive waiters. Yet, POLLFREE *must* wake up all waiters. epoll and aio poll are fortunately not affected by this, but it's very fragile. Thus, the new function wake_up_pollfree() has been introduced. Convert binder to use wake_up_pollfree(). Reported-by: Linus Torvalds Fixes: f5cb779ba163 ("ANDROID: binder: remove waitqueue when thread exits.") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers --- drivers/android/binder.c | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index cffbe57a8e086..c75fb600740cc 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -4422,23 +4422,20 @@ static int binder_thread_release(struct binder_proc *proc, __release(&t->lock); /* - * If this thread used poll, make sure we remove the waitqueue - * from any epoll data structures holding it with POLLFREE. - * waitqueue_active() is safe to use here because we're holding - * the inner lock. + * If this thread used poll, make sure we remove the waitqueue from any + * poll data structures holding it. */ - if ((thread->looper & BINDER_LOOPER_STATE_POLL) && - waitqueue_active(&thread->wait)) { - wake_up_poll(&thread->wait, EPOLLHUP | POLLFREE); - } + if (thread->looper & BINDER_LOOPER_STATE_POLL) + wake_up_pollfree(&thread->wait); binder_inner_proc_unlock(thread->proc); /* - * This is needed to avoid races between wake_up_poll() above and - * and ep_remove_waitqueue() called for other reasons (eg the epoll file - * descriptor being closed); ep_remove_waitqueue() holds an RCU read - * lock, so we can be sure it's done after calling synchronize_rcu(). + * This is needed to avoid races between wake_up_pollfree() above and + * someone else removing the last entry from the queue for other reasons + * (e.g. ep_remove_wait_queue() being called due to an epoll file + * descriptor being closed). Such other users hold an RCU read lock, so + * we can be sure they're done after we call synchronize_rcu(). */ if (thread->looper & BINDER_LOOPER_STATE_POLL) synchronize_rcu(); -- 2.34.1