* [PATCH] powerpc: Fix deadlock with mmu_hash_lock in hash_page_sync
2008-03-30 21:28 mmu_hash_lock deadlock causes kernel stuck at 2.6.21 SMP powerpc 32bit Gaash Hazan
@ 2008-03-30 21:49 ` Benjamin Herrenschmidt
0 siblings, 0 replies; 2+ messages in thread
From: Benjamin Herrenschmidt @ 2008-03-30 21:49 UTC (permalink / raw)
To: gaash-ppclnx; +Cc: linuxppc-dev, Paul Mackerras, Gilad Ben-Yossef
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 handler, taking it must be done with
interrupts off. However, hash_page_sync() appear 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>
---
Please test and report asap thought it's probably too late for
2.6.25, it can still go into stable later on.
Index: linux-work/arch/powerpc/mm/hash_low_32.S
===================================================================
--- linux-work.orig/arch/powerpc/mm/hash_low_32.S 2008-03-31 08:42:56.000000000 +1100
+++ linux-work/arch/powerpc/mm/hash_low_32.S 2008-03-31 08:45:05.000000000 +1100
@@ -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)
- blr
-#endif
+ mtmsr r10
+ blr
+#endif /* CONFIG_SMP */
/*
* Load a PTE into the hash table, if possible.
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] powerpc: Fix deadlock with mmu_hash_lock in hash_page_sync
[not found] <8C22373EA650AF40928EEA0C188D62D206C71041@xmb-ams-338.emea.cisco.com>
@ 2008-03-31 8:30 ` Gaash Hazan
0 siblings, 0 replies; 2+ messages in thread
From: Gaash Hazan @ 2008-03-31 8:30 UTC (permalink / raw)
To: Benjamin Herrenschmidt
Cc: linuxppc-dev, Paul Mackerras, gaash-ppclnx, Gilad Ben-Yossef
> -----Original Message-----
> From: Benjamin Herrenschmidt
> [mailto:benh@kernel•crashing.org]
> Sent: Monday, March 31, 2008 0:49
> To: gaash-ppclnx@gaashh•com
> Cc: linuxppc-dev@ozlabs•org; Gilad Ben-Yossef; Paul
> Mackerras
> Subject: [PATCH] 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
> handler, taking it must be done with interrupts off.
> However,
> hash_page_sync() appear 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>
> ---
>
> Please test and report asap thought it's probably
> too late for 2.6.25,
> it can still go into stable later on.
>
Thank you for the quick acknowledgment and patch.
Patch works well.
Thanks,
Gaash
^ permalink raw reply [flat|nested] 2+ messages in thread
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2008-03-31 8:30 ` [PATCH] powerpc: Fix deadlock with mmu_hash_lock in hash_page_sync Gaash Hazan
2008-03-30 21:28 mmu_hash_lock deadlock causes kernel stuck at 2.6.21 SMP powerpc 32bit Gaash Hazan
2008-03-30 21:49 ` [PATCH] powerpc: Fix deadlock with mmu_hash_lock in hash_page_sync Benjamin Herrenschmidt
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