Commit fcafddec authored by Len Brown's avatar Len Brown Committed by Ingo Molnar

x86/smpboot: Fix CPU #1 boot timeout

The following commit:

  a9bcaa02 ("x86/smpboot: Remove SIPI delays from cpu_up()")

Caused some Intel Core2 processors to time-out when bringing up CPU #1,
resulting in the missing of that CPU after bootup.

That patch reduced the SIPI delays from udelay() 300, 200 to udelay() 0,
0 on modern processors.

Several Intel(R) Core(TM)2 systems failed to bring up CPU #1 10/10 times
after that change.

Increasing either of the SIPI delays to udelay(1) results in
success. So here we increase both to udelay(10).  While this may
be 20x slower than the absolute minimum, it is still 20x to 30x
faster than the original code.
Tested-by: default avatarDonald Parsons <dparsons@brightdsl.net>
Tested-by: default avatarShane <shrybman@teksavvy.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dparsons@brightdsl.net
Cc: shrybman@teksavvy.com
Link: http://lkml.kernel.org/r/6dd554ee8945984d85aafb2ad35793174d068af0.1444968087.git.len.brown@intel.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f1ccd249
......@@ -660,7 +660,9 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip)
/*
* Give the other CPU some time to accept the IPI.
*/
if (init_udelay)
if (init_udelay == 0)
udelay(10);
else
udelay(300);
pr_debug("Startup point 1\n");
......@@ -671,7 +673,9 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip)
/*
* Give the other CPU some time to accept the IPI.
*/
if (init_udelay)
if (init_udelay == 0)
udelay(10);
else
udelay(200);
if (maxlvt > 3) /* Due to the Pentium erratum 3AP. */
......
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