From patchwork Tue Dec 12 08:07:45 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Vacek X-Patchwork-Id: 13488655 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="combx/Cs" Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 58C39DE for ; Tue, 12 Dec 2023 00:08:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1702368479; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WXqf2vh/WJNQMCP9P3WEFWf2Hyjzd2SEqm/uvxIkz6Y=; b=combx/CsHrh+k8BWFHkVZa/4UotYcSkmjJ/gw0Fwp7Y8x8TTXPUX1MvlfLK6l7gP1bt8eF 42d74sbcCM131OyuEO1oSP+UpIgWKg9xOS4wkEbefV/J0uvwUfQAskec6J9xCXp97n2U+m t2VnmRvp4hLLkknq1lsR15eFd7L06zg= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-28-0rMprEnIO2CiBXKl6z94Hg-1; Tue, 12 Dec 2023 03:07:56 -0500 X-MC-Unique: 0rMprEnIO2CiBXKl6z94Hg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B41AA85A588; Tue, 12 Dec 2023 08:07:55 +0000 (UTC) Received: from metal.redhat.com (unknown [10.45.224.23]) by smtp.corp.redhat.com (Postfix) with ESMTP id 17ECD492BE6; Tue, 12 Dec 2023 08:07:53 +0000 (UTC) From: Daniel Vacek To: Jason Gunthorpe , Leon Romanovsky Cc: linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, Daniel Vacek , Yuya Fujita-bishamonten Subject: [PATCH v2] IB/ipoib: Fix mcast list locking Date: Tue, 12 Dec 2023 09:07:45 +0100 Message-ID: <20231212080746.1528802-1-neelx@redhat.com> In-Reply-To: <20231211130426.1500427-1-neelx@redhat.com> References: <20231211130426.1500427-1-neelx@redhat.com> Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Releasing the `priv->lock` while iterating the `priv->multicast_list` in `ipoib_mcast_join_task()` opens a window for `ipoib_mcast_dev_flush()` to remove the items while in the middle of iteration. If the mcast is removed while the lock was dropped, the for loop spins forever resulting in a hard lockup (as was reported on RHEL 4.18.0-372.75.1.el8_6 kernel): Task A (kworker/u72:2 below) | Task B (kworker/u72:0 below) -----------------------------------+----------------------------------- ipoib_mcast_join_task(work) | ipoib_ib_dev_flush_light(work) spin_lock_irq(&priv->lock) | __ipoib_ib_dev_flush(priv, ...) list_for_each_entry(mcast, | ipoib_mcast_dev_flush(dev = priv->dev) &priv->multicast_list, list) | ipoib_mcast_join(dev, mcast) | spin_unlock_irq(&priv->lock) | | spin_lock_irqsave(&priv->lock, flags) | list_for_each_entry_safe(mcast, tmcast, | &priv->multicast_list, list) | list_del(&mcast->list); | list_add_tail(&mcast->list, &remove_list) | spin_unlock_irqrestore(&priv->lock, flags) spin_lock_irq(&priv->lock) | | ipoib_mcast_remove_list(&remove_list) (Here, `mcast` is no longer on the | list_for_each_entry_safe(mcast, tmcast, `priv->multicast_list` and we keep | remove_list, list) spinning on the `remove_list` of | >>> wait_for_completion(&mcast->done) the other thread which is blocked | and the list is still valid on | it's stack.) Fix this by keeping the lock held and changing to GFP_ATOMIC to prevent eventual sleeps. Unfortunately we could not reproduce the lockup and confirm this fix but based on the code review I think this fix should address such lockups. crash> bc 31 PID: 747 TASK: ff1c6a1a007e8000 CPU: 31 COMMAND: "kworker/u72:2" --- [exception RIP: ipoib_mcast_join_task+0x1b1] RIP: ffffffffc0944ac1 RSP: ff646f199a8c7e00 RFLAGS: 00000002 RAX: 0000000000000000 RBX: ff1c6a1a04dc82f8 RCX: 0000000000000000 work (&priv->mcast_task{,.work}) RDX: ff1c6a192d60ac68 RSI: 0000000000000286 RDI: ff1c6a1a04dc8000 &mcast->list RBP: ff646f199a8c7e90 R8: ff1c699980019420 R9: ff1c6a1920c9a000 R10: ff646f199a8c7e00 R11: ff1c6a191a7d9800 R12: ff1c6a192d60ac00 mcast R13: ff1c6a1d82200000 R14: ff1c6a1a04dc8000 R15: ff1c6a1a04dc82d8 dev priv (&priv->lock) &priv->multicast_list (aka head) ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 --- --- #5 [ff646f199a8c7e00] ipoib_mcast_join_task+0x1b1 at ffffffffc0944ac1 [ib_ipoib] #6 [ff646f199a8c7e98] process_one_work+0x1a7 at ffffffff9bf10967 crash> rx ff646f199a8c7e68 ff646f199a8c7e68: ff1c6a1a04dc82f8 <<< work = &priv->mcast_task.work crash> list -hO ipoib_dev_priv.multicast_list ff1c6a1a04dc8000 (empty) crash> ipoib_dev_priv.mcast_task.work.func,mcast_mutex.owner.counter ff1c6a1a04dc8000 mcast_task.work.func = 0xffffffffc0944910 , mcast_mutex.owner.counter = 0xff1c69998efec000 crash> b 8 PID: 8 TASK: ff1c69998efec000 CPU: 33 COMMAND: "kworker/u72:0" -- #3 [ff646f1980153d50] wait_for_completion+0x96 at ffffffff9c7d7646 #4 [ff646f1980153d90] ipoib_mcast_remove_list+0x56 at ffffffffc0944dc6 [ib_ipoib] #5 [ff646f1980153de8] ipoib_mcast_dev_flush+0x1a7 at ffffffffc09455a7 [ib_ipoib] #6 [ff646f1980153e58] __ipoib_ib_dev_flush+0x1a4 at ffffffffc09431a4 [ib_ipoib] #7 [ff646f1980153e98] process_one_work+0x1a7 at ffffffff9bf10967 crash> rx ff646f1980153e68 ff646f1980153e68: ff1c6a1a04dc83f0 <<< work = &priv->flush_light crash> ipoib_dev_priv.flush_light.func,broadcast ff1c6a1a04dc8000 flush_light.func = 0xffffffffc0943820 , broadcast = 0x0, The mcast(s) on the `remove_list` (the remaining part of the ex `priv->multicast_list`): crash> list -s ipoib_mcast.done.done ipoib_mcast.list -H ff646f1980153e10 | paste - - ff1c6a192bd0c200 done.done = 0x0, ff1c6a192d60ac00 done.done = 0x0, Reported-by: Yuya Fujita-bishamonten Signed-off-by: Daniel Vacek --- drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c index 5b3154503bf4..bca80fe07584 100644 --- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c @@ -531,21 +531,17 @@ static int ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast) if (test_bit(IPOIB_MCAST_FLAG_SENDONLY, &mcast->flags)) rec.join_state = SENDONLY_FULLMEMBER_JOIN; } - spin_unlock_irq(&priv->lock); multicast = ib_sa_join_multicast(&ipoib_sa_client, priv->ca, priv->port, - &rec, comp_mask, GFP_KERNEL, + &rec, comp_mask, GFP_ATOMIC, ipoib_mcast_join_complete, mcast); - spin_lock_irq(&priv->lock); if (IS_ERR(multicast)) { ret = PTR_ERR(multicast); ipoib_warn(priv, "ib_sa_join_multicast failed, status %d\n", ret); /* Requeue this join task with a backoff delay */ __ipoib_mcast_schedule_join_thread(priv, mcast, 1); clear_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags); - spin_unlock_irq(&priv->lock); complete(&mcast->done); - spin_lock_irq(&priv->lock); } return 0; }