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 1861CC433F5 for ; Mon, 18 Apr 2022 22:54:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233655AbiDRW5S (ORCPT ); Mon, 18 Apr 2022 18:57:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44382 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233305AbiDRW4t (ORCPT ); Mon, 18 Apr 2022 18:56:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E0C0F2CE2C; Mon, 18 Apr 2022 15:54:03 -0700 (PDT) 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 8A5F8B81136; Mon, 18 Apr 2022 22:54:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42828C385A1; Mon, 18 Apr 2022 22:54:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650322441; bh=tPyCRwdFs1UacCDWo6gPWFP2J8tgNjkdVtTI/kMjO/s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TcUbXgjE7VF1cqmzO0nZknf3hCOB6m2pLrkKrPBeLeT9duKCb0DbzbydFSa50sG0k hcRX7uV/VAEGuvQEbnPMYNOHsXJCGFJCmzNXAl+2EWzwzQ54ak8oC8qeQCpinYhuAs CqtBVAiJGo8D2iuyaWcHhM4USdLCm898Bq+B2NFawfme1LKeRZQKO+IQodD93TI4vR v5VbPp/rAodcE/QRsmIGNmkOYd7xequfoHJKHDylT4mOfQBdsqmhh6t3ICVkAlYxJB rjgwNxfhHMDWRwSYlruRV7piO/azxnadspi1KG+660ywzzP9uLiZmM1VuOot1pvtlW ugsjYlo/5TWUg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id E554E5C0A0D; Mon, 18 Apr 2022 15:54:00 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, "Paul E. McKenney" , Rik van Riel , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Sebastian Andrzej Siewior , Juergen Gross Subject: [PATCH rcu 04/11] kernel/smp: Provide boot-time timeout for CSD lock diagnostics Date: Mon, 18 Apr 2022 15:53:52 -0700 Message-Id: <20220418225359.3945217-4-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220418225345.GA3945110@paulmck-ThinkPad-P17-Gen-1> References: <20220418225345.GA3945110@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Debugging of problems involving insanely long-running SMI handlers proceeds better if the CSD-lock timeout can be adjusted. This commit therefore provides a new smp.csd_lock_timeout kernel boot parameter that specifies the timeout in milliseconds. The default remains at the previously hard-coded value of five seconds. Cc: Rik van Riel Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Sebastian Andrzej Siewior Cc: Juergen Gross Signed-off-by: Paul E. McKenney --- Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++++ kernel/smp.c | 7 +++++-- 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 3f1cc5e317ed..645c4c001b16 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5377,6 +5377,17 @@ smart2= [HW] Format: [,[,...,]] + smp.csd_lock_timeout= [KNL] + Specify the period of time in milliseconds + that smp_call_function() and friends will wait + for a CPU to release the CSD lock. This is + useful when diagnosing bugs involving CPUs + disabling interrupts for extended periods + of time. Defaults to 5,000 milliseconds, and + setting a value of zero disables this feature. + This feature may be more efficiently disabled + using the csdlock_debug- kernel parameter. + smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port smsc-ircc2.ircc_sir= [HW] SIR base I/O port diff --git a/kernel/smp.c b/kernel/smp.c index 01a7c1706a58..d82439bac401 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -183,7 +183,9 @@ static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func); static DEFINE_PER_CPU(void *, cur_csd_info); static DEFINE_PER_CPU(struct cfd_seq_local, cfd_seq_local); -#define CSD_LOCK_TIMEOUT (5ULL * NSEC_PER_SEC) +static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */ +module_param(csd_lock_timeout, ulong, 0444); + static atomic_t csd_bug_count = ATOMIC_INIT(0); static u64 cfd_seq; @@ -329,6 +331,7 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 * u64 ts2, ts_delta; call_single_data_t *cpu_cur_csd; unsigned int flags = READ_ONCE(csd->node.u_flags); + unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC; if (!(flags & CSD_FLAG_LOCK)) { if (!unlikely(*bug_id)) @@ -341,7 +344,7 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 * ts2 = sched_clock(); ts_delta = ts2 - *ts1; - if (likely(ts_delta <= CSD_LOCK_TIMEOUT)) + if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns <= 0)) return false; firsttime = !*bug_id; -- 2.31.1.189.g2e36527f23