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 <linux@xxxxxxxxxxxxxxxx> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
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); }
Attachment:
config.vexpress-qemu.gz
Description: application/gzip
