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[67.170.153.23]) by mx.google.com with ESMTPSA id om2sm37086369pbb.34.2013.07.22.11.21.20 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 22 Jul 2013 11:21:21 -0700 (PDT) Message-ID: <51ED781F.6060300@linaro.org> Date: Mon, 22 Jul 2013 11:21:19 -0700 From: John Stultz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7 MIME-Version: 1.0 To: Stephen Boyd Subject: Re: [PATCH v4 03/17] sched_clock: Use an hrtimer instead of timer References: <1374189690-10810-1-git-send-email-sboyd@codeaurora.org> <1374189690-10810-4-git-send-email-sboyd@codeaurora.org> In-Reply-To: <1374189690-10810-4-git-send-email-sboyd@codeaurora.org> X-Gm-Message-State: ALoCoQk8pQSrjEj423/Po+nAFHc4kGTZbZgSGP8F/9jk1vwQrCxIAfXk56qlQe6Dwg5YLO3MtJnH X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130722_142144_418852_216EC2E5 X-CRM114-Status: UNSURE ( 8.70 ) X-CRM114-Notice: Please train this message. X-Spam-Score: -2.6 (--) Cc: Russell King , linux-arm-msm@vger.kernel.org, Will Deacon , linux-kernel@vger.kernel.org, Christopher Covington , Catalin Marinas , Thomas Gleixner , linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-5.6 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On 07/18/2013 04:21 PM, Stephen Boyd wrote: > In the next patch we're going to increase the number of bits that > the generic sched_clock can handle to be greater than 32. With > more than 32 bits the wraparound time can be larger than what can > fit into the units that msecs_to_jiffies takes (unsigned int). > Luckily, the wraparound is initially calculated in nanoseconds > which we can easily use with hrtimers, so switch to using an > hrtimer. > > Cc: Russell King > Signed-off-by: Stephen Boyd Hrmm. So in my testing (under qemu), this patch causes bootup to hang. qemu-system-arm -kernel zImage-arm -M vexpress-a9 -cpu cortex-a9 -nographic -m 1024 -append 'root=/dev/mmcblk0p2 rw mem=1024M raid=noautodetect console=ttyAMA0,38400n8 rootwait vmalloc=256MB devtmpfs.mount=0' -sd test-arm.img -redir tcp:4300::22 Config file attached. I haven't gotten a chance to look very closely, but it seems the folowing patch resolves the issue. I'm not sure if we're seeing callers to setup_sched_clock happen after sched_clock_postinit or what, but it probably needs another look over. thanks -john diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c index a269890b..c018ffc 100644 --- a/kernel/time/sched_clock.c +++ b/kernel/time/sched_clock.c @@ -138,12 +138,6 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lluns\n", bits, r, r_unit, res, wrap); - /* - * Start the timer to keep sched_clock() properly updated and - * sets the initial epoch. - */ - hrtimer_init(&sched_clock_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); - sched_clock_timer.function = sched_clock_poll; update_sched_clock(); /* @@ -175,6 +169,13 @@ void __init sched_clock_postinit(void) setup_sched_clock(jiffy_sched_clock_read, 32, HZ); update_sched_clock(); + + /* + * Start the timer to keep sched_clock() properly updated and + * sets the initial epoch. + */ + hrtimer_init(&sched_clock_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + sched_clock_timer.function = sched_clock_poll; hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL); }