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authorJiri Slaby <jslaby@suse.cz>2017-01-19 12:47:30 +0100
committerIngo Molnar <mingo@kernel.org>2017-01-22 10:03:12 +0100
commit4c45c5167c9563b1a2eee3e2fe954621355e4ca8 (patch)
tree4a248dcdcdc4783cb0173be4d30825601e698a68
parentd852d39432f5d9822dd0ea8760573448338caf41 (diff)
x86/timer: Make delay() work during early bootup
When a panic happens during bootup, "Rebooting in X seconds.." is shown, but reboot happens immediatelly. It is because panic() uses mdelay() and mdelay() calls __const_udelay() immediately, which does not work while booting. The per_cpu cpu_info.loops_per_jiffy value is not initialized yet, so __const_udelay() actually multiplies the number of loops by zero. This results in __const_udelay() to delay the execution only by a nanosecond or so. So check whether cpu_info.loops_per_jiffy is zero and use loops_per_jiffy in that case. mdelay() will not be so precise without proper calibration, but it works relatively well. Before: [ 0.170039] delaying 100ms [ 0.170828] done After [ 0.214042] delaying 100ms [ 0.313974] done I do not think the added check matters given we are about to spin the processor in the next few hundred cycles. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20170119114730.2670-1-jslaby@suse.cz [ Minor edits. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/x86/lib/delay.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c
index 073d1f1a620b..a8e91ae89fb3 100644
--- a/arch/x86/lib/delay.c
+++ b/arch/x86/lib/delay.c
@@ -156,13 +156,13 @@ EXPORT_SYMBOL(__delay);
inline void __const_udelay(unsigned long xloops)
{
+ unsigned long lpj = this_cpu_read(cpu_info.loops_per_jiffy) ? : loops_per_jiffy;
int d0;
xloops *= 4;
asm("mull %%edx"
:"=d" (xloops), "=&a" (d0)
- :"1" (xloops), "0"
- (this_cpu_read(cpu_info.loops_per_jiffy) * (HZ/4)));
+ :"1" (xloops), "0" (lpj * (HZ / 4)));
__delay(++xloops);
}