Commit b991f05f authored Mar 31, 2008 by Benjamin Herrenschmidt Committed by Paul Mackerras Apr 03, 2008

[POWERPC] Fix deadlock with mmu_hash_lock in hash_page_sync



hash_page_sync() takes and releases the low level mmu hash
lock in order to sync with other processors disposing of page
tables.  Because that lock can be needed to service hash misses
triggered by interrupt handlers, taking it must be done with
interrupts off.  However, hash_page_sync() appears to be called
with interrupts enabled, thus causing occasional deadlocks.

We fix it by making sure hash_page_sync() masks interrupts while
holding the lock.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

parent ff3da2e0

arch/powerpc/mm/hash_low_32.S

+6 −2

Original line number	Diff line number	Diff line
		@@ -44,6 +44,9 @@ mmu_hash_lock:
		#ifdef CONFIG_SMP
		.text
		_GLOBAL(hash_page_sync)
		mfmsr r10
		rlwinm r0,r10,0,17,15 /* clear bit 16 (MSR_EE) */
		mtmsr r0
		lis r8,mmu_hash_lock@h
		ori r8,r8,mmu_hash_lock@l
		lis r0,0x0fff
		@@ -60,8 +63,9 @@ _GLOBAL(hash_page_sync)
		eieio
		li r0,0
		stw r0,0(r8)
		mtmsr r10
		blr
		#endif
		#endif /* CONFIG_SMP */

		/*
		* Load a PTE into the hash table, if possible.