Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH] x86: make delay work in earlier stages | Date | Thu, 19 Jan 2017 12:47:30 +0100 |
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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 internally __const_udelay which is broken 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, but it works relatively good. From the original (mdelay in rest_init): [ 0.170039] delaying 100ms [ 0.170828] done I get: [ 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> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: <x86@kernel.org> --- arch/x86/lib/delay.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c index 073d1f1a620b..aca0988f0e14 100644 --- a/arch/x86/lib/delay.c +++ b/arch/x86/lib/delay.c @@ -156,13 +156,14 @@ EXPORT_SYMBOL(__delay); inline void __const_udelay(unsigned long xloops) { + unsigned long lpf = 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" (lpf * (HZ / 4))); __delay(++xloops); } -- 2.11.0
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