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Mon, 2 Nov 2026 14:54:15 -0800 From: Kal Cutter Conley To: Trond Myklebust , Anna Schumaker , Chuck Lever , Jeff Layton , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman CC: Kal Cutter Conley , , , Subject: [PATCH v2] sunrpc: fix lost wakeups when stopping service threads Date: Mon, 2 Nov 2026 23:53:58 +0100 Message-ID: <20261102225358.414367-1-kalcutterc@nvidia.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261030130629.103716-1-kalcutterc@nvidia.com> References: <20261030130629.103716-1-kalcutterc@nvidia.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: rnnvmail203.nvidia.com (10.129.68.9) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MW2PEPF00014679:EE_|CY1PR12MB9558:EE_ X-MS-Office365-Filtering-Correlation-Id: 70b3791b-39c3-4464-87e9-08df39344779 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|82310400026|36860700016|1800799024|376014|23010399003|18002099003|22082099003|10067099003|56012099006|261102123227099003|261102130727099003|13003099007|261009223027099003|921020|261022105027099003|261028144727099003|261021121427099003|261022075727099003|11063799006|261026140227099003|261026121527099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(7416014)(82310400026)(36860700016)(1800799024)(376014)(23010399003)(18002099003)(22082099003)(10067099003)(56012099006)(261102123227099003)(261102130727099003)(13003099007)(261009223027099003)(921020)(261022105027099003)(261028144727099003)(261021121427099003)(261022075727099003)(11063799006)(261026140227099003)(261026121527099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: OGxGvS+BHgBm+PowF+ZqmnkhrH5corGMZVWpNSMxRN8ISUPBOijywGoXbJ16/bMT9jVFUJa97zMbRDFSsaekF0u2YohDkoXCo9f1kP/y9+/86M2mhiNETbqNq8R0yE1wAHWZo3Q22Q5qhEkGUI0VJiX7ZgjWwoJfAquWPd10buDKmNacjM7VshTWmACxgzv3wDu6a1lCARiyNGPNR83AiqCFvAdMtNuB2x6tvVL0osWq9EeoF2Sa142LNo13DjSUJCx+hm5AMA/fsE7WdfF1iJIU+xy83bPuBgjE/ksMPW/f6YmM54qfAN2KIdGsjeG7PP88/4lVqXzWsL9rvfb8jCpMrbJRwuSI9WFhqMqqIj0MasCrcRwXm2pLTGjacv6qUPQNrG01ZYOocP5tca8AqpI+fz3jqvuCm/fs7lGj2fUFBQbGoaOkBA5UgK9ooYJ/ X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Nov 2026 22:54:40.9199 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 70b3791b-39c3-4464-87e9-08df39344779 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: MW2PEPF00014679.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY1PR12MB9558 Stopping NFS can leave rpc.nfsd 0 in an uninterruptible wait with this stack: svc_stop_kthreads [sunrpc] svc_set_num_threads [sunrpc] nfsd_svc [nfsd] write_threads [nfsd] nfsctl_transaction_write [nfsd] SP_NEED_VICTIM and SP_VICTIM_REMAINS remain set while all remaining nfsd threads sleep in svc_recv() and none has RQ_VICTIM set. The stop request is published with unordered set_bit() operations. svc_pool_wake_idle_thread() checks the idle list and task state before calling wake_up_process(). If it sees an empty list or TASK_RUNNING, it skips the wakeup and its memory barrier. The requester can therefore miss a sleeping worker while that worker misses the stop request. Use smp_mb__after_atomic() after the flag updates in svc_stop_kthreads() and svc_wake_up() to order work publication before both lockless checks, even when no wakeup occurs. Pair with set_current_state() and llist_add() in svc_thread_wait_for_work(), so the worker observes the pending work or the requester observes the idle worker and wakes it. Fixes: 60749cbe3d8a ("sunrpc: change sp_nrthreads from atomic_t to unsigned int.") Signed-off-by: Kal Cutter Conley --- Changes in v2: - Move the barrier into svc_stop_kthreads() and svc_wake_up(), using smp_mb__after_atomic(). This avoids adding a redundant barrier on the transport enqueue path. v1: https://lore.kernel.org/r/20261030130629.103716-1-kalcutterc@nvidia.com net/sunrpc/svc.c | 7 +++++++ net/sunrpc/svc_xprt.c | 5 +++++ 2 files changed, 12 insertions(+) diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c index af8d87c1de83..76232774646c 100644 --- a/net/sunrpc/svc.c +++ b/net/sunrpc/svc.c @@ -29,6 +29,8 @@ #include #include +#include + #include #include "fail.h" @@ -784,6 +786,11 @@ svc_stop_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs) do { set_bit(SP_VICTIM_REMAINS, &pool->sp_flags); set_bit(SP_NEED_VICTIM, &pool->sp_flags); + /* + * Order flag updates before the idle list and task state checks. + * Pairs with the barriers in svc_thread_wait_for_work(). + */ + smp_mb__after_atomic(); svc_pool_wake_idle_thread(pool); wait_on_bit(&pool->sp_flags, SP_VICTIM_REMAINS, TASK_IDLE); nrservs++; diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index 076c624fe675..868e3da57b6c 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -632,6 +632,11 @@ void svc_wake_up(struct svc_serv *serv) struct svc_pool *pool = &serv->sv_pools[0]; set_bit(SP_TASK_PENDING, &pool->sp_flags); + /* + * Order flag updates before the idle list and task state checks. + * Pairs with the barriers in svc_thread_wait_for_work(). + */ + smp_mb__after_atomic(); svc_pool_wake_idle_thread(pool); } EXPORT_SYMBOL_GPL(svc_wake_up); base-commit: 2d3259f652bb0f1d137ccabecac6763da05064ec -- 2.53.0