From patchwork Wed Jun 22 10:55:50 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Russell King - ARM Linux X-Patchwork-Id: 904432 Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p5MAvV9c000697 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 22 Jun 2011 10:57:57 GMT Received: from canuck.infradead.org ([2001:4978:20e::1]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1QZL7T-0002Pq-Ri; Wed, 22 Jun 2011 10:57:15 +0000 Received: from localhost ([127.0.0.1] helo=canuck.infradead.org) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1QZL7T-0005oK-Fw; Wed, 22 Jun 2011 10:57:15 +0000 Received: from [2002:4e20:1eda::1] (helo=caramon.arm.linux.org.uk) by canuck.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1QZL7O-0005o1-RZ for linux-arm-kernel@lists.infradead.org; Wed, 22 Jun 2011 10:57:12 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=arm.linux.org.uk; s=caramon; h=Sender:Content-Type:MIME-Version:Message-ID:Subject:Cc:To:From:Date; bh=olq1p+ZSYEEQ4VIq+PeJ/BqjLtcG9PwSv235KvqWDx8=; b=jmIsqQJxDgi2k4GnB2vwGHl9mqcAAY6VyLSUHOtqptr/0BDmttrgtTlmAmD5uYaG/SxTa+7FOAZuCDarZTlxIWjMjRZCpzBxWt2RwCLxEBbNQtj4RfmpOpO2GwQnIjT6cVje15OHUSzbzloFNPqP0G716kDqHY1sh2Pb/qjs9Yg=; Received: from n2100.arm.linux.org.uk ([2002:4e20:1eda:1:214:fdff:fe10:4f86]) by caramon.arm.linux.org.uk with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.72) (envelope-from ) id 1QZL67-0003c9-RU; Wed, 22 Jun 2011 11:55:52 +0100 Received: from linux by n2100.arm.linux.org.uk with local (Exim 4.72) (envelope-from ) id 1QZL66-00031Z-FQ; Wed, 22 Jun 2011 11:55:50 +0100 Date: Wed, 22 Jun 2011 11:55:50 +0100 From: Russell King - ARM Linux To: Linus Torvalds , Andrew Morton Subject: [PATCH] Fix CPU spinlock lockups on secondary CPU bringup Message-ID: <20110622105550.GQ23234@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.19 (2009-01-05) X-CRM114-Version: 20090807-BlameThorstenAndJenny ( TRE 0.7.6 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20110622_065711_462711_226B9CEF X-CRM114-Status: GOOD ( 17.32 ) X-Spam-Score: 1.2 (+) X-Spam-Report: SpamAssassin version 3.3.1 on canuck.infradead.org summary: Content analysis details: (1.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 1.3 RDNS_NONE Delivered to internal network by a host with no rDNS Cc: linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter2.kernel.org [140.211.167.43]); Wed, 22 Jun 2011 10:57:57 +0000 (UTC) From: Russell King Secondary CPU bringup typically calls calibrate_delay() during its initialization. However, calibrate_delay() modifies a global variable (loops_per_jiffy) used for udelay() and __delay(). A side effect of 71c696b1 (calibrate: extract fall-back calculation into own helper) introduced in the 2.6.39 merge window means that we end up with a substantial period where loops_per_jiffy is zero. This causes the spinlock debugging code to malfunction: u64 loops = loops_per_jiffy * HZ; for (;;) { for (i = 0; i < loops; i++) { if (arch_spin_trylock(&lock->raw_lock)) return; __delay(1); } ... } by never calling arch_spin_trylock() - resulting in the CPU locking up in an infinite loop inside __spin_lock_debug(). Work around this by only writing to loops_per_jiffy only once we have completed all the calibration decisions. Tested-by: Santosh Shilimkar Signed-off-by: Russell King Cc: (2.6.39-stable) --- Better solutions (such as omitting the calibration for secondary CPUs, or arranging for calibrate_delay() to return the LPJ value and leave it to the caller to decide where to store it) are a possibility, but would be much more invasive into each architecture. I think this is the best solution for -rc and stable, but it should be revisited for the next merge window. init/calibrate.c | 14 ++++++++------ 1 files changed, 8 insertions(+), 6 deletions(-) diff --git a/init/calibrate.c b/init/calibrate.c index 2568d22..aae2f40 100644 --- a/init/calibrate.c +++ b/init/calibrate.c @@ -245,30 +245,32 @@ static unsigned long __cpuinit calibrate_delay_converge(void) void __cpuinit calibrate_delay(void) { + unsigned long lpj; static bool printed; if (preset_lpj) { - loops_per_jiffy = preset_lpj; + lpj = preset_lpj; if (!printed) pr_info("Calibrating delay loop (skipped) " "preset value.. "); } else if ((!printed) && lpj_fine) { - loops_per_jiffy = lpj_fine; + lpj = lpj_fine; pr_info("Calibrating delay loop (skipped), " "value calculated using timer frequency.. "); - } else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) { + } else if ((lpj = calibrate_delay_direct()) != 0) { if (!printed) pr_info("Calibrating delay using timer " "specific routine.. "); } else { if (!printed) pr_info("Calibrating delay loop... "); - loops_per_jiffy = calibrate_delay_converge(); + lpj = calibrate_delay_converge(); } if (!printed) pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n", - loops_per_jiffy/(500000/HZ), - (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy); + lpj/(500000/HZ), + (lpj/(5000/HZ)) % 100, lpj); + loops_per_jiffy = lpj; printed = true; }