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Commit f1ccd249 authored by Len Brown's avatar Len Brown Committed by Ingo Molnar
Browse files

x86/smpboot: Fix cpu_init_udelay=10000 corner case boot parameter misbehavior 



For legacy machines cpu_init_udelay defaults to 10,000.
For modern machines it is set to 0.

The user should be able to set cpu_init_udelay to
any value on the cmdline, including 10,000.

Before this patch, that was seen as "unchanged from default"
and thus on a modern machine, the user request was ignored
and the delay was set to 0.

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/de363cdbbcfcca1d22569683f7eb9873e0177251.1444968087.git.len.brown@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c0ff971e

arch/x86/kernel/smpboot.c

+5 −2
Original line number Diff line number Diff line
@@ -509,7 +509,7 @@ void __inquire_remote_apic(int apicid) 
 */

#define UDELAY_10MS_DEFAULT 10000



static unsigned int init_udelay = UDELAY_10MS_DEFAULT;

static unsigned int init_udelay = INT_MAX;



static int __init cpu_init_udelay(char *str)

{
@@ -522,13 +522,16 @@ early_param("cpu_init_udelay", cpu_init_udelay); 
static void __init smp_quirk_init_udelay(void)

{

	/* if cmdline changed it from default, leave it alone */

	if (init_udelay != UDELAY_10MS_DEFAULT)

	if (init_udelay != INT_MAX)

		return;



	/* if modern processor, use no delay */

	if (((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) && (boot_cpu_data.x86 == 6)) ||

	    ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && (boot_cpu_data.x86 >= 0xF)))

		init_udelay = 0;



	/* else, use legacy delay */

	init_udelay = UDELAY_10MS_DEFAULT;

}



/*