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GET /api/patches/2197121/?format=api
{ "id": 2197121, "url": "http://patchwork.ozlabs.org/api/patches/2197121/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260217-alpha-v1-2-0dcc708c9db3@rsg.ci.i.u-tokyo.ac.jp/", "project": { "id": 14, "url": "http://patchwork.ozlabs.org/api/projects/14/?format=api", "name": "QEMU Development", "link_name": "qemu-devel", "list_id": "qemu-devel.nongnu.org", "list_email": "qemu-devel@nongnu.org", "web_url": "", "scm_url": "", "webscm_url": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260217-alpha-v1-2-0dcc708c9db3@rsg.ci.i.u-tokyo.ac.jp>", "list_archive_url": null, "date": "2026-02-17T06:34:30", "name": "[2/2] Reapply \"rcu: Unify force quiescent state\"", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "f2ab21fb0a93e5a842a7e9a56d406d28f82d7f33", "submitter": { "id": 90980, "url": "http://patchwork.ozlabs.org/api/people/90980/?format=api", "name": "Akihiko Odaki", "email": "odaki@rsg.ci.i.u-tokyo.ac.jp" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260217-alpha-v1-2-0dcc708c9db3@rsg.ci.i.u-tokyo.ac.jp/mbox/", "series": [ { "id": 492379, "url": "http://patchwork.ozlabs.org/api/series/492379/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=492379", "date": "2026-02-17T06:34:29", "name": "Reapply \"rcu: Unify force quiescent state\"", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/492379/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2197121/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2197121/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=fail reason=\"key not found in DNS\" header.d=rsg.ci.i.u-tokyo.ac.jp\n header.i=@rsg.ci.i.u-tokyo.ac.jp header.a=rsa-sha256 header.s=rs20250326\n header.b=I6ibcv2t;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)" ], "Received": [ "from lists.gnu.org (lists.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fFVJj6jg0z1xwD\n\tfor <incoming@patchwork.ozlabs.org>; Tue, 17 Feb 2026 17:35:49 +1100 (AEDT)", "from localhost ([::1] helo=lists1p.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.90_1)\n\t(envelope-from <qemu-devel-bounces@nongnu.org>)\n\tid 1vsEfr-0006Yg-DB; Tue, 17 Feb 2026 01:35:07 -0500", "from eggs.gnu.org ([2001:470:142:3::10])\n by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from <odaki@rsg.ci.i.u-tokyo.ac.jp>)\n id 1vsEfp-0006Wj-EK\n for qemu-devel@nongnu.org; Tue, 17 Feb 2026 01:35:05 -0500", "from www3579.sakura.ne.jp ([49.212.243.89])\n by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from <odaki@rsg.ci.i.u-tokyo.ac.jp>)\n id 1vsEfn-0004T5-AB\n for qemu-devel@nongnu.org; Tue, 17 Feb 2026 01:35:05 -0500", "from h205.csg.ci.i.u-tokyo.ac.jp (h205.csg.ci.i.u-tokyo.ac.jp\n [133.11.54.205]) (authenticated bits=0)\n by www3579.sakura.ne.jp (8.16.1/8.16.1) with ESMTPSA id 61H6Yfkh030238\n (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO);\n Tue, 17 Feb 2026 15:34:43 +0900 (JST)\n (envelope-from odaki@rsg.ci.i.u-tokyo.ac.jp)" ], "DKIM-Signature": "a=rsa-sha256; bh=H6ljr/jVCWKO176X63ceZZm1uT0oaOP95joZ3kpX6PE=;\n c=relaxed/relaxed; d=rsg.ci.i.u-tokyo.ac.jp;\n h=From:Date:Subject:Message-Id:To;\n s=rs20250326; t=1771310083; v=1;\n b=I6ibcv2tH/cxK1WAVj7w1vVYPuCyblBvxIhjoB9Ie8jdOVkH7Iz7UCpjek2k267A\n q6TfDi5WVhibb4on388be7fReS4UQm688TGNFlLJa3PH10VyPS+hDwfARpF9Frqy\n QaDlfw6tPYGcmGBKRpiT5tcWj0D6jsjWLhRiK5nzbSJFFCiqV09v4HBo3sIA/lbL\n dG9N6i85rjXDJu1s8Komvd2367xxxekagRoJKZT4/RjsFHzT+LW9GOFxr2hBGqrK\n EY0Fg9BvbfekKXaGftjg8PRJIzujRhtQN+ZSU8JUEO7amNED8e5FbHFXaNQlUVOI\n ImkI4FP8N7rnaty3Gn3BiA==", "From": "Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>", "Date": "Tue, 17 Feb 2026 15:34:30 +0900", "Subject": "[PATCH 2/2] Reapply \"rcu: Unify force quiescent state\"", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=\"utf-8\"", "Content-Transfer-Encoding": "7bit", "Message-Id": "<20260217-alpha-v1-2-0dcc708c9db3@rsg.ci.i.u-tokyo.ac.jp>", "References": "<20260217-alpha-v1-0-0dcc708c9db3@rsg.ci.i.u-tokyo.ac.jp>", "In-Reply-To": "<20260217-alpha-v1-0-0dcc708c9db3@rsg.ci.i.u-tokyo.ac.jp>", "To": "qemu-devel@nongnu.org", "Cc": "Richard Henderson <richard.henderson@linaro.org>,\n Paolo Bonzini <pbonzini@redhat.com>, Thomas Huth <thuth@redhat.com>,\n\t=?utf-8?q?Alex_Benn=C3=A9e?= <alex.bennee@linaro.org>,\n Jim MacArthur <jim.macarthur@linaro.org>,\n Yodel Eldar <yodel.eldar@yodel.dev>,\n Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>", "X-Mailer": "b4 0.15-dev-67ece", "Received-SPF": "pass client-ip=49.212.243.89;\n envelope-from=odaki@rsg.ci.i.u-tokyo.ac.jp; helo=www3579.sakura.ne.jp", "X-Spam_score_int": "-16", "X-Spam_score": "-1.7", "X-Spam_bar": "-", "X-Spam_report": "(-1.7 / 5.0 requ) BAYES_00=-1.9, DKIM_INVALID=0.1,\n DKIM_SIGNED=0.1, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001,\n RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001,\n SPF_PASS=-0.001 autolearn=no autolearn_force=no", "X-Spam_action": "no action", "X-BeenThere": "qemu-devel@nongnu.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "qemu development <qemu-devel.nongnu.org>", "List-Unsubscribe": "<https://lists.nongnu.org/mailman/options/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>", "List-Archive": "<https://lists.nongnu.org/archive/html/qemu-devel>", "List-Post": "<mailto:qemu-devel@nongnu.org>", "List-Help": "<mailto:qemu-devel-request@nongnu.org?subject=help>", "List-Subscribe": "<https://lists.nongnu.org/mailman/listinfo/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=subscribe>", "Errors-To": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org", "Sender": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org" }, "content": "This reverts commit ddb4d9d1748681cfde824d765af6cda4334fcce3.\n\nThe commit says:\n> This reverts commit 55d98e3edeeb17dd8445db27605d2b34f4c3ba85.\n>\n> The commit introduced a regression in the replay functional test\n> on alpha (tests/functional/alpha/test_replay.py), that causes CI\n> failures regularly. Thus revert this change until someone has\n> figured out what is going wrong here.\n\nReapply the change as alpha is fixed.\n\nSigned-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>\n---\n util/rcu.c | 79 ++++++++++++++++++++++++++++++++++++++++----------------------\n 1 file changed, 51 insertions(+), 28 deletions(-)", "diff": "diff --git a/util/rcu.c b/util/rcu.c\nindex b703c86f15a3..acac9446ea98 100644\n--- a/util/rcu.c\n+++ b/util/rcu.c\n@@ -43,10 +43,14 @@\n #define RCU_GP_LOCKED (1UL << 0)\n #define RCU_GP_CTR (1UL << 1)\n \n+\n+#define RCU_CALL_MIN_SIZE 30\n+\n unsigned long rcu_gp_ctr = RCU_GP_LOCKED;\n \n QemuEvent rcu_gp_event;\n static int in_drain_call_rcu;\n+static int rcu_call_count;\n static QemuMutex rcu_registry_lock;\n static QemuMutex rcu_sync_lock;\n \n@@ -76,15 +80,29 @@ static void wait_for_readers(void)\n {\n ThreadList qsreaders = QLIST_HEAD_INITIALIZER(qsreaders);\n struct rcu_reader_data *index, *tmp;\n+ int sleeps = 0;\n+ bool forced = false;\n \n for (;;) {\n- /* We want to be notified of changes made to rcu_gp_ongoing\n- * while we walk the list.\n+ /*\n+ * Force the grace period to end and wait for it if any of the\n+ * following heuristical conditions are satisfied:\n+ * - A decent number of callbacks piled up.\n+ * - It timed out.\n+ * - It is in a drain_call_rcu() call.\n+ *\n+ * Otherwise, periodically poll the grace period, hoping it ends\n+ * promptly.\n */\n- qemu_event_reset(&rcu_gp_event);\n+ if (!forced &&\n+ (qatomic_read(&rcu_call_count) >= RCU_CALL_MIN_SIZE ||\n+ sleeps >= 5 || qatomic_read(&in_drain_call_rcu))) {\n+ forced = true;\n \n- QLIST_FOREACH(index, ®istry, node) {\n- qatomic_set(&index->waiting, true);\n+ QLIST_FOREACH(index, ®istry, node) {\n+ notifier_list_notify(&index->force_rcu, NULL);\n+ qatomic_set(&index->waiting, true);\n+ }\n }\n \n /* Here, order the stores to index->waiting before the loads of\n@@ -106,8 +124,6 @@ static void wait_for_readers(void)\n * get some extra futex wakeups.\n */\n qatomic_set(&index->waiting, false);\n- } else if (qatomic_read(&in_drain_call_rcu)) {\n- notifier_list_notify(&index->force_rcu, NULL);\n }\n }\n \n@@ -115,7 +131,8 @@ static void wait_for_readers(void)\n break;\n }\n \n- /* Wait for one thread to report a quiescent state and try again.\n+ /*\n+ * Sleep for a while and try again.\n * Release rcu_registry_lock, so rcu_(un)register_thread() doesn't\n * wait too much time.\n *\n@@ -133,7 +150,20 @@ static void wait_for_readers(void)\n * rcu_registry_lock is released.\n */\n qemu_mutex_unlock(&rcu_registry_lock);\n- qemu_event_wait(&rcu_gp_event);\n+\n+ if (forced) {\n+ qemu_event_wait(&rcu_gp_event);\n+\n+ /*\n+ * We want to be notified of changes made to rcu_gp_ongoing\n+ * while we walk the list.\n+ */\n+ qemu_event_reset(&rcu_gp_event);\n+ } else {\n+ g_usleep(10000);\n+ sleeps++;\n+ }\n+\n qemu_mutex_lock(&rcu_registry_lock);\n }\n \n@@ -173,15 +203,11 @@ void synchronize_rcu(void)\n }\n }\n \n-\n-#define RCU_CALL_MIN_SIZE 30\n-\n /* Multi-producer, single-consumer queue based on urcu/static/wfqueue.h\n * from liburcu. Note that head is only used by the consumer.\n */\n static struct rcu_head dummy;\n static struct rcu_head *head = &dummy, **tail = &dummy.next;\n-static int rcu_call_count;\n static QemuEvent rcu_call_ready_event;\n \n static void enqueue(struct rcu_head *node)\n@@ -259,30 +285,27 @@ static void *call_rcu_thread(void *opaque)\n rcu_register_thread();\n \n for (;;) {\n- int tries = 0;\n- int n = qatomic_read(&rcu_call_count);\n+ int n;\n \n- /* Heuristically wait for a decent number of callbacks to pile up.\n+ /*\n * Fetch rcu_call_count now, we only must process elements that were\n * added before synchronize_rcu() starts.\n */\n- while (n == 0 || (n < RCU_CALL_MIN_SIZE && ++tries <= 5)) {\n- g_usleep(10000);\n- if (n == 0) {\n- qemu_event_reset(&rcu_call_ready_event);\n- n = qatomic_read(&rcu_call_count);\n- if (n == 0) {\n+ for (;;) {\n+ qemu_event_reset(&rcu_call_ready_event);\n+ n = qatomic_read(&rcu_call_count);\n+ if (n) {\n+ break;\n+ }\n+\n #if defined(CONFIG_MALLOC_TRIM)\n- malloc_trim(4 * 1024 * 1024);\n+ malloc_trim(4 * 1024 * 1024);\n #endif\n- qemu_event_wait(&rcu_call_ready_event);\n- }\n- }\n- n = qatomic_read(&rcu_call_count);\n+ qemu_event_wait(&rcu_call_ready_event);\n }\n \n- qatomic_sub(&rcu_call_count, n);\n synchronize_rcu();\n+ qatomic_sub(&rcu_call_count, n);\n bql_lock();\n while (n > 0) {\n node = try_dequeue();\n", "prefixes": [ "2/2" ] }