Re: [patch] sched: fix scheduling latencies in mtrr.c

[Ingo Molnar]

> fix scheduling latencies in the MTRR-setting codepath.
> Also, fix bad bug: MTRR's _must_ be set with interrupts disabled!

patch attached ...

caveat: one of the wbinvd() removals is correct i believe, but the other
one might be problematic. It doesnt seem logical to do a wbinvd() at
that point though ...

	Ingo

fix scheduling latencies in the MTRR-setting codepath.
Also, fix bad bug: MTRR's _must_ be set with interrupts disabled!

Signed-off-by: Ingo Molnar <mingo@xxxxxxx>

--- linux/arch/i386/kernel/cpu/mtrr/generic.c.orig	
+++ linux/arch/i386/kernel/cpu/mtrr/generic.c	
@@ -240,11 +240,14 @@ static void prepare_set(void)
 	/*  Note that this is not ideal, since the cache is only flushed/disabled
 	   for this CPU while the MTRRs are changed, but changing this requires
 	   more invasive changes to the way the kernel boots  */
-	spin_lock(&set_atomicity_lock);
+	/*
+	 * Since we are disabling the cache dont allow any interrupts - they
+	 * would run extremely slow and would only increase the pain:
+	 */
+	spin_lock_irq(&set_atomicity_lock);
 
 	/*  Enter the no-fill (CD=1, NW=0) cache mode and flush caches. */
 	cr0 = read_cr0() | 0x40000000;	/* set CD flag */
-	wbinvd();
 	write_cr0(cr0);
 	wbinvd();
 
@@ -266,8 +269,7 @@ static void prepare_set(void)
 
 static void post_set(void)
 {
-	/*  Flush caches and TLBs  */
-	wbinvd();
+	/*  Flush TLBs (no need to flush caches - they are disabled)  */
 	__flush_tlb();
 
 	/* Intel (P6) standard MTRRs */
@@ -279,7 +281,7 @@ static void post_set(void)
 	/*  Restore value of CR4  */
 	if ( cpu_has_pge )
 		write_cr4(cr4);
-	spin_unlock(&set_atomicity_lock);
+	spin_unlock_irq(&set_atomicity_lock);
 }
 
 static void generic_set_all(void)