Commit-ID: bf3304d996fbb993bad6be09cafde39cc2db72bb Gitweb: http://git.kernel.org/tip/bf3304d996fbb993bad6be09cafde39cc2db72bb Author: Jiri Slaby <[email protected]> AuthorDate: Thu, 19 Jan 2017 12:47:30 +0100 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 20 Jan 2017 09:45:22 +0100
x86/timer: Make delay() 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 is does not work while booting. The per_cpu cpu_info.loops_per_jiffy 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 <[email protected]> Reviewed-by: Andy Shevchenko <[email protected]> Acked-by: Thomas Gleixner <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Link: http://lkml.kernel.org/r/[email protected] [ Minor edits. ] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/lib/delay.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c index 073d1f1..a8e91ae 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); }
