x86/mm: Fix pgd_lock deadlock

x86/mm: Fix pgd_lock deadlock

It's forbidden to take the page_table_lock with the irq disabled
or if there's contention the IPIs (for tlb flushes) sent with
the page_table_lock held will never run leading to a deadlock.

Nobody takes the pgd_lock from irq context so the _irqsave can be
removed.

Signed-off-by: Andrea Arcangeli <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Tested-by: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: <[email protected]>
LKML-Reference: <201102162345[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>