sched/preempt, mm/kmap, MIPS: Disable preemption in kmap_coherent() e…

…xplicitly

k(un)map_coherent relies on pagefault_disable() to also disable
preemption.

Let's make this explicit, to prepare for pagefault_disable() not
touching preemption anymore.

This patch is based on a patch by Yang Shi on the -rt tree:
"k{un}map_coherent are just called when cpu_has_dc_aliases == 1 with VIPT
cache. However, actually, the most modern MIPS processors have PIPT dcache
without dcache alias issue. In such case, k{un}map_atomic will be called
with preempt enabled."

Reviewed-and-tested-by: Thomas Gleixner <[email protected]>
Signed-off-by: David Hildenbrand <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: [email protected]
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

arch/mips/mm/init.c

@@ -90,6 +90,7 @@ static void *__kmap_pgprot(struct page *page, unsigned long addr, pgprot_t prot)
 
 	BUG_ON(Page_dcache_dirty(page));
 
+	preempt_disable();
 	pagefault_disable();
 	idx = (addr >> PAGE_SHIFT) & (FIX_N_COLOURS - 1);
 	idx += in_interrupt() ? FIX_N_COLOURS : 0;
@@ -152,6 +153,7 @@ void kunmap_coherent(void)
 	write_c0_entryhi(old_ctx);
 	local_irq_restore(flags);
 	pagefault_enable();
+	preempt_enable();
 }
 
 void copy_user_highpage(struct page *to, struct page *from,