From 853b160aaafbe27d6304c8832bb7340d57c6b04e Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@kernel.org>
Date: Wed, 13 May 2015 08:40:49 +0200
Subject: [PATCH] Revert f5d6a52f5111 ("x86/smpboot: Skip delays during SMP
 initialization similar to Xen")
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Huang Ying reported x86 boot hangs due to this commit.

Turns out that the change, despite its changelog, does more
than just change timeouts: it also changes the way we
assert/deassert INIT via the APIC_DM_INIT IPI, in the x2apic
case it skips the deassert step.

This is historically fragile code and the patch did not
improve it, so revert these changes.

This commit:

  1a744cb356c5 ("x86/smp/boot: Remove 10ms delay from cpu_up() on modern processors")

independently removes the worst of the delays (the 10 msec delay).

The remaining delays can be addressed one by one, combined
with careful testing.

Reported-by: Huang Ying <ying.huang@intel.com>
Cc: Anthony Liguori <aliguori@amazon.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Gang Wei <gang.wei@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan H. Schönherr <jschoenh@amazon.de>
Cc: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Deegan <tim@xen.org>
Link: http://lkml.kernel.org/r/1430732554-7294-1-git-send-email-jschoenh@amazon.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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