From mboxrd@z Thu Jan 1 00:00:00 1970 From: john.stultz@linaro.org (John Stultz) Date: Mon, 22 Jul 2013 11:21:19 -0700 Subject: [PATCH v4 03/17] sched_clock: Use an hrtimer instead of timer In-Reply-To: <1374189690-10810-4-git-send-email-sboyd@codeaurora.org> References: <1374189690-10810-1-git-send-email-sboyd@codeaurora.org> <1374189690-10810-4-git-send-email-sboyd@codeaurora.org> Message-ID: <51ED781F.6060300@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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); } -------------- next part -------------- A non-text attachment was scrubbed... Name: config.vexpress-qemu.gz Type: application/gzip Size: 19985 bytes Desc: not available URL: