From nobody Mon Feb 9 13:00:29 2026 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0A5962EA731 for ; Sat, 20 Dec 2025 08:35:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766219704; cv=pass; b=FlpPuR2ng6C9i2n8aVB/MCqPZksJD0Rs3v5/ktgdzqT4LJxdDMVEVHCLE9tGie1frfKYpBMx5i5UGYE/pHqmOI51YJNoi9V89dQy0YXn3pCIQezXpHeqiQKcYySgqnjPpElC/wge0a1De50RUPhSg6LyupVUb6zYpo1O7suyAIM= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766219704; c=relaxed/simple; bh=UpBQjzOv2zWJm0MiE40rFexes1ffQA8ZykCSkFpddhA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=N/oM4doityU/tJ0ce4LAKgu18n/MdYPkSQ20vFUmGAeKY6+dcfVBXq54S0Pl31kTAyKjnFY6jOZCXWvwPgRwtJbNiaS88P67JquXDloAMhXKsgp7AYBDdwsKaLiqMaO2sZQxKKo1Iy0M3WntQlvbiIK3sEmMrUI6SkwRUoHDti0= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux.beauty; spf=pass smtp.mailfrom=linux.beauty; dkim=pass (1024-bit key) header.d=linux.beauty header.i=me@linux.beauty header.b=sgu8AE7P; arc=pass smtp.client-ip=136.143.188.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux.beauty Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.beauty Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.beauty header.i=me@linux.beauty header.b="sgu8AE7P" ARC-Seal: i=1; a=rsa-sha256; t=1766219694; cv=none; d=zohomail.com; s=zohoarc; b=F6xkMlVw2L1Bipdj2Ma32EA2LTgqTXvZ9e4y8LkQnmUQzoRpP9XeaOniTte9zppx2b1SXQmsvag0iZtNVHlw5zwxAIuonCIVpwJbYCTUKjPgQEae0tjBpO0CudhMSXBGLU4RbX567L9G3sHVT18Vcj/UqadXHEB5IKDQPCD8K1w= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1766219694; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=5InwQq38W8dhaMny4s4eL6hBKvOJdW7iE44wBOaPYsE=; b=PRVrZb0ZhZh11g9TpfV147HpUCr0r8iCh4OTOiJaolNvv/ezoPmOanHsYBXBpzxr95aBGOeVYeVRcRDwxyHPBKfLtaF6RvLWUwrxiJYuiyPCFBSW5FBgC3GPsTpHW0jIFeGD/Tkg7VvkPeLF/+PEOvrgUs70fWKAma30ywTIkCg= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=linux.beauty; spf=pass smtp.mailfrom=me@linux.beauty; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1766219694; s=zmail; d=linux.beauty; i=me@linux.beauty; h=From:From:To:To:Cc:Cc:Subject:Subject:Date:Date:Message-ID:In-Reply-To:References:MIME-Version:Content-Transfer-Encoding:Message-Id:Reply-To; bh=5InwQq38W8dhaMny4s4eL6hBKvOJdW7iE44wBOaPYsE=; b=sgu8AE7PCzvD6PyY8+lKT2wTsvgH8kM5EHNDkkmDpypDyXArHO0sWLnBdQ5UWJ7d tPa8nw5vNv+lykg23+U8Focltd2xfdj+1h5Qg4yBcS1Xkw3Yq/LEY9kFZ15/SzFb87Q QgapBF8KNi864CVJCKxwmBFLzOmaUi9e1u4ZV9cM= Received: by mx.zohomail.com with SMTPS id 1766219692437326.47273936198314; Sat, 20 Dec 2025 00:34:52 -0800 (PST) From: Li Chen To: Pankaj Gupta , Dan Williams , Vishal Verma , Dave Jiang , Ira Weiny , virtualization@lists.linux.dev, nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Li Chen Subject: [PATCH 1/4] nvdimm: virtio_pmem: always wake -ENOSPC waiters Date: Sat, 20 Dec 2025 16:34:37 +0800 Message-ID: <20251220083441.313737-2-me@linux.beauty> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251220083441.313737-1-me@linux.beauty> References: <20251220083441.313737-1-me@linux.beauty> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMailClient: External Content-Type: text/plain; charset="utf-8" virtio_pmem_host_ack() reclaims virtqueue descriptors with virtqueue_get_buf(). The -ENOSPC waiter wakeup is tied to completing the returned token. If token completion is skipped for any reason, reclaimed descriptors may not wake a waiter and the submitter may sleep forever waiting for a free slot. Always wake one -ENOSPC waiter for each virtqueue completion before touching the returned token. Use READ_ONCE()/WRITE_ONCE() for the wait_event() flags (done and wq_buf_avail). They are observed by waiters without pmem_lock, so make the accesses explicit single loads/stores and avoid compiler reordering/caching across the wait/wake paths. Signed-off-by: Li Chen --- drivers/nvdimm/nd_virtio.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-) diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c index c3f07be4aa22..6f9890361d0b 100644 --- a/drivers/nvdimm/nd_virtio.c +++ b/drivers/nvdimm/nd_virtio.c @@ -9,26 +9,33 @@ #include "virtio_pmem.h" #include "nd.h" =20 +static void virtio_pmem_wake_one_waiter(struct virtio_pmem *vpmem) +{ + struct virtio_pmem_request *req_buf; + + if (list_empty(&vpmem->req_list)) + return; + + req_buf =3D list_first_entry(&vpmem->req_list, + struct virtio_pmem_request, list); + list_del_init(&req_buf->list); + WRITE_ONCE(req_buf->wq_buf_avail, true); + wake_up(&req_buf->wq_buf); +} + /* The interrupt handler */ void virtio_pmem_host_ack(struct virtqueue *vq) { struct virtio_pmem *vpmem =3D vq->vdev->priv; - struct virtio_pmem_request *req_data, *req_buf; + struct virtio_pmem_request *req_data; unsigned long flags; unsigned int len; =20 spin_lock_irqsave(&vpmem->pmem_lock, flags); while ((req_data =3D virtqueue_get_buf(vq, &len)) !=3D NULL) { - req_data->done =3D true; + virtio_pmem_wake_one_waiter(vpmem); + WRITE_ONCE(req_data->done, true); wake_up(&req_data->host_acked); - - if (!list_empty(&vpmem->req_list)) { - req_buf =3D list_first_entry(&vpmem->req_list, - struct virtio_pmem_request, list); - req_buf->wq_buf_avail =3D true; - wake_up(&req_buf->wq_buf); - list_del(&req_buf->list); - } } spin_unlock_irqrestore(&vpmem->pmem_lock, flags); } @@ -58,7 +65,7 @@ static int virtio_pmem_flush(struct nd_region *nd_region) if (!req_data) return -ENOMEM; =20 - req_data->done =3D false; + WRITE_ONCE(req_data->done, false); init_waitqueue_head(&req_data->host_acked); init_waitqueue_head(&req_data->wq_buf); INIT_LIST_HEAD(&req_data->list); @@ -79,12 +86,12 @@ static int virtio_pmem_flush(struct nd_region *nd_regio= n) GFP_ATOMIC)) =3D=3D -ENOSPC) { =20 dev_info(&vdev->dev, "failed to send command to virtio pmem device, no f= ree slots in the virtqueue\n"); - req_data->wq_buf_avail =3D false; + WRITE_ONCE(req_data->wq_buf_avail, false); list_add_tail(&req_data->list, &vpmem->req_list); spin_unlock_irqrestore(&vpmem->pmem_lock, flags); =20 /* A host response results in "host_ack" getting called */ - wait_event(req_data->wq_buf, req_data->wq_buf_avail); + wait_event(req_data->wq_buf, READ_ONCE(req_data->wq_buf_avail)); spin_lock_irqsave(&vpmem->pmem_lock, flags); } err1 =3D virtqueue_kick(vpmem->req_vq); @@ -98,7 +105,7 @@ static int virtio_pmem_flush(struct nd_region *nd_region) err =3D -EIO; } else { /* A host response results in "host_ack" getting called */ - wait_event(req_data->host_acked, req_data->done); + wait_event(req_data->host_acked, READ_ONCE(req_data->done)); err =3D le32_to_cpu(req_data->resp.ret); } =20 --=20 2.51.0