Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932978Ab3GVSpp (ORCPT ); Mon, 22 Jul 2013 14:45:45 -0400 Received: from smtp.codeaurora.org ([198.145.11.231]:39870 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932757Ab3GVSpn (ORCPT ); Mon, 22 Jul 2013 14:45:43 -0400 Message-ID: <51ED7DD5.8010000@codeaurora.org> Date: Mon, 22 Jul 2013 11:45:41 -0700 From: Stephen Boyd User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:17.0) Gecko/20130620 Thunderbird/17.0.7 MIME-Version: 1.0 To: John Stultz CC: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Thomas Gleixner , Russell King , Catalin Marinas , Will Deacon , Christopher Covington 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> <51ED781F.6060300@linaro.org> In-Reply-To: <51ED781F.6060300@linaro.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5248 Lines: 125 On 07/22/13 11:21, John Stultz wrote: > 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); > } > > Hmm. Is it too early to use hrtimers? Moving the hrtimer_start() into sched_clock_register() also causes the same crash. [ 0.000000] Unable to handle kernel NULL pointer dereference at virtual address 00000000 [ 0.000000] pgd = c0004000 [ 0.000000] [00000000] *pgd=00000000 [ 0.000000] Internal error: Oops: 5 [#1] SMP ARM [ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.11.0-rc1-00017-gecfb8ad-dirty #69 [ 0.000000] task: c063b600 ti: c0630000 task.ti: c0630000 [ 0.000000] PC is at _raw_spin_lock_irqsave+0xc/0x48 [ 0.000000] LR is at lock_hrtimer_base+0x20/0x4c [ 0.000000] pc : [] lr : [] psr: a00001d3 [ 0.000000] sp : c0631f40 ip : 00000001 fp : 00000000 [ 0.000000] r10: 00000000 r9 : 410fc090 r8 : c06e44c0 [ 0.000000] r7 : c063c508 r6 : c0631f7c r5 : c06e44c0 r4 : c062e538 [ 0.000000] r3 : 00000024 r2 : 00000000 r1 : c0631f7c r0 : a00001d3 [ 0.000000] Flags: NzCv IRQs off FIQs off Mode SVC_32 ISA ARM Segment kernel [ 0.000000] Control: 10c5387d Table: 6000406a DAC: 00000015 [ 0.000000] Process swapper/0 (pid: 0, stack limit = 0xc0630238) [ 0.000000] Stack: (0xc0631f40 to 0xc0632000) [ 0.000000] 1f40: c06be640 c06150a0 c0f05940 c005f344 00000000 00989680 755552dc 00000024 [ 0.000000] 1f60: c063cd80 c0441354 755552dc 00000024 00000000 00000000 c063cd80 00000002 [ 0.000000] 1f80: c0441354 c06be640 c06150a0 c0f05940 c063c508 6000406a 410fc090 00000000 [ 0.000000] 1fa0: 00000000 c005f74c 00000000 00000001 00000001 00000000 00000000 c05e5984 [ 0.000000] 1fc0: 00000001 c05c2e38 00000001 c05c06e0 ffffffff ffffffff c05c02ec 00000000 [ 0.000000] 1fe0: 00000000 c06150a0 10c5387d c0638418 c061509c 60008074 00000000 00000000 [ 0.000000] [] (_raw_spin_lock_irqsave+0xc/0x48) from [] (lock_hrtimer_base+0x20/0x4c) [ 0.000000] [] (lock_hrtimer_base+0x20/0x4c) from [] (__hrtimer_start_range_ns+0x1c/0x3d8) [ 0.000000] [] (__hrtimer_start_range_ns+0x1c/0x3d8) from [] (hrtimer_start+0x20/0x28) [ 0.000000] [] (hrtimer_start+0x20/0x28) from [] (sched_clock_postinit+0x44/0x5c) [ 0.000000] [] (sched_clock_postinit+0x44/0x5c) from [] (start_kernel+0x1d0/0x31c) [ 0.000000] [] (start_kernel+0x1d0/0x31c) from [<60008074>] (0x60008074) [ 0.000000] Code: e12fff1e e1a02000 e10f0000 f10c0080 (e1923f9f) -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/