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| author | Jiri Slaby <jslaby@suse.cz> | 2017-01-19 12:47:30 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-01-22 10:03:12 +0100 |
| commit | 4c45c5167c9563b1a2eee3e2fe954621355e4ca8 (patch) | |
| tree | 4a248dcdcdc4783cb0173be4d30825601e698a68 /arch/x86/lib/delay.c | |
| parent | timerqueue: Use rb_entry_safe() instead of open-coding it (diff) | |
| download | linux-4c45c5167c9563b1a2eee3e2fe954621355e4ca8.tar.xz linux-4c45c5167c9563b1a2eee3e2fe954621355e4ca8.zip | |
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>
Diffstat (limited to 'arch/x86/lib/delay.c')
| -rw-r--r-- | arch/x86/lib/delay.c | 4 |
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); } |