From: gdavis@mvista.com (George G. Davis)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC/PATCH v4 6/7] ARM: ARM11 MPCore: DMA_CACHE_RWFO operations are not preempt safe
Date: Tue, 18 Oct 2011 19:26:02 -0400 [thread overview]
Message-ID: <20111018232602.GA237@mvista.com> (raw)
In-Reply-To: <alpine.LFD.2.02.1110181715120.17040@xanadu.home>
Hello,
On Tue, Oct 18, 2011 at 05:28:45PM -0400, Nicolas Pitre wrote:
> On Tue, 18 Oct 2011, gdavis at mvista.com wrote:
>
> > @@ -241,6 +247,13 @@ v6_dma_inv_range:
> > blo 1b
> > mov r0, #0
> > mcr p15, 0, r0, c7, c10, 4 @ drain write buffer
> > +#if defined(CONFIG_DMA_CACHE_RWFO) && defined(CONFIG_PREEMPT)
> > + str r3, [ip, #TI_PREEMPT] @ restore preempt count
> > + teq r3, #0 @ preempt count == 0?
> > + ldreq r3, [ip, #TI_FLAGS] @ load flags if yes
> > + tst r3, #_TIF_NEED_RESCHED @ need resched?
> > + bne preempt_schedule @ ret via preempt_schedule
>
> This is buggy. If the preempt count is _not_ zero, you end up not
> loading the TI_FLAGS bits and testing _TIF_NEED_RESCHED against that
> non-zero preempt count.
Sigh, yep. FWIW, I had the following before submitting this but dropped
it due to brain failure rereading the code - convinced myself that the
movne was redundant:
diff --git a/arch/arm/mm/cache-v6.S b/arch/arm/mm/cache-v6.S
index af055dc..5c6ce38 100644
--- a/arch/arm/mm/cache-v6.S
+++ b/arch/arm/mm/cache-v6.S
@@ -285,6 +287,7 @@ v6_dma_inv_range:
str r3, [ip, #TI_PREEMPT] @ restore preempt count
teq r3, #0 @ preempt count == 0?
ldreq r3, [ip, #TI_FLAGS] @ load flags if yes
+ movne r3, #0 @ force flags to 0
tst r3, #_TIF_NEED_RESCHED @ need resched?
bne preempt_schedule @ ret via preempt_schedule
#endif
@@ -321,6 +324,7 @@ v6_dma_clean_range:
str r3, [ip, #TI_PREEMPT] @ restore preempt count
teq r3, #0 @ preempt count == 0?
ldreq r3, [ip, #TI_FLAGS] @ load flags if yes
+ movne r3, #0 @ force flags to 0
tst r3, #_TIF_NEED_RESCHED @ need resched?
bne preempt_schedule @ ret via preempt_schedule
#endif
@@ -362,6 +366,7 @@ ENTRY(v6_dma_flush_range)
str r3, [ip, #TI_PREEMPT] @ restore preempt count
teq r3, #0 @ preempt count == 0?
ldreq r3, [ip, #TI_FLAGS] @ load flags if yes
+ movne r3, #0 @ force flags to 0
tst r3, #_TIF_NEED_RESCHED @ need resched?
bne preempt_schedule @ ret via preempt_schedule
#endif
In this case, I think preempt_{disable,enable} is the better option
(over interrupt disable/enable) due to variable DMA buffer sizes.
Thanks!
--
Regards,
George
>
>
> Nicolas
next prev parent reply other threads:[~2011-10-18 23:26 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-20 13:43 parallel load of modules on an ARM multicore EXTERNAL Waechtler Peter (Fa. TCP, CM-AI/PJ-CF31)
2011-06-21 15:50 ` Catalin Marinas
2011-06-23 14:39 ` AW: " EXTERNAL Waechtler Peter (Fa. TCP, CM-AI/PJ-CF31)
2011-06-23 14:52 ` Catalin Marinas
2011-06-23 15:12 ` Russell King - ARM Linux
2011-06-23 15:34 ` Catalin Marinas
2011-06-23 17:02 ` Catalin Marinas
2011-06-23 15:20 ` AW: " EXTERNAL Waechtler Peter (Fa. TCP, CM-AI/PJ-CF31)
2011-07-07 4:25 ` George G. Davis
2011-10-20 4:04 ` George G. Davis
2011-09-22 7:29 ` George G. Davis
2011-09-22 8:52 ` Catalin Marinas
2011-10-06 4:29 ` George G. Davis
2011-10-06 5:08 ` [RFC/PATCH 0/7] ARM: ARM11 MPCore preemption/task migration cache coherency fixups gdavis at mvista.com
2011-10-06 5:08 ` [RFC/PATCH 1/7] ARM: ARM11 MPCore: pgd_alloc is not preempt safe gdavis at mvista.com
2011-10-06 16:35 ` Russell King - ARM Linux
2011-10-06 19:38 ` George G. Davis
2011-10-06 5:08 ` [RFC/PATCH 2/7] ARM: ARM11 MPCore: pte_alloc_one{, _kernel} are " gdavis at mvista.com
2011-10-06 5:08 ` [RFC/PATCH 3/7] ARM: ARM11 MPCore: {clean, flush}_pmd_entry " gdavis at mvista.com
2011-10-06 5:08 ` [RFC/PATCH 4/7] ARM: ARM11 MPCore: clean_dcache_area is " gdavis at mvista.com
2011-10-06 5:08 ` [RFC/PATCH 5/7] ARM: Move get_thread_info macro definition to <asm/assembler.h> gdavis at mvista.com
2011-10-06 5:08 ` [RFC/PATCH 6/7] ARM: ARM11 MPCore: DMA_CACHE_RWFO operations are not preempt safe gdavis at mvista.com
2011-10-06 16:40 ` Russell King - ARM Linux
2011-10-06 19:41 ` George G. Davis
2011-10-06 5:08 ` [RFC/PATCH 7/7] ARM: ARM11 MPCore: cpu_v6_set_pte_ext is " gdavis at mvista.com
2011-10-06 7:46 ` Russell King - ARM Linux
2011-10-06 12:35 ` George G. Davis
2011-10-07 2:38 ` [RFC/PATCH v2 0/7] ARM11 MPCore: preemption/task migration cache coherency fixups gdavis at mvista.com
2011-10-07 2:38 ` [RFC/PATCH 1/7] ARM: ARM11 MPCore: pgd_alloc is not preempt safe gdavis at mvista.com
2011-10-07 2:38 ` [RFC/PATCH 2/7] ARM: ARM11 MPCore: pte_alloc_one{, _kernel} are " gdavis at mvista.com
2011-10-07 7:47 ` [RFC/PATCH 2/7] ARM: ARM11 MPCore: pte_alloc_one{,_kernel} " Russell King - ARM Linux
2011-10-07 15:31 ` [RFC/PATCH 2/7] ARM: ARM11 MPCore: pte_alloc_one{, _kernel} " George G. Davis
2011-10-07 2:38 ` [RFC/PATCH 3/7] ARM: ARM11 MPCore: {clean, flush}_pmd_entry " gdavis at mvista.com
2011-10-11 9:53 ` [RFC/PATCH 3/7] ARM: ARM11 MPCore: {clean,flush}_pmd_entry " Catalin Marinas
2011-10-12 2:34 ` [RFC/PATCH 3/7] ARM: ARM11 MPCore: {clean, flush}_pmd_entry " George G. Davis
2011-10-13 14:31 ` [RFC/PATCH 3/7] ARM: ARM11 MPCore: {clean,flush}_pmd_entry " Russell King - ARM Linux
2011-10-14 1:34 ` [RFC/PATCH 3/7] ARM: ARM11 MPCore: {clean, flush}_pmd_entry " George G. Davis
2011-10-07 2:38 ` [RFC/PATCH 4/7] ARM: ARM11 MPCore: clean_dcache_area is " gdavis at mvista.com
2011-10-07 2:38 ` [RFC/PATCH 5/7] ARM: Move get_thread_info macro definition to <asm/assembler.h> gdavis at mvista.com
2011-10-11 9:56 ` Catalin Marinas
2011-10-12 6:04 ` gdavis at mvista.com
2011-10-13 14:34 ` Russell King - ARM Linux
2011-10-13 14:49 ` Catalin Marinas
2011-10-13 14:53 ` Russell King - ARM Linux
2011-10-14 1:46 ` George G. Davis
2011-10-14 1:44 ` George G. Davis
2011-10-14 1:42 ` George G. Davis
2011-10-14 2:54 ` Nicolas Pitre
2011-10-14 12:56 ` George G. Davis
2011-10-07 2:38 ` [RFC/PATCH 6/7] ARM: ARM11 MPCore: DMA_CACHE_RWFO operations are not preempt safe gdavis at mvista.com
2011-10-07 2:38 ` [RFC/PATCH 7/7] ARM: ARM11 MPCore: cpu_v6_set_pte_ext is " gdavis at mvista.com
2011-10-07 16:26 ` [RFC/PATCH v3 0/7] ARM11 MPCore: preemption/task migration cache coherency fixups gdavis at mvista.com
2011-10-07 16:26 ` [RFC/PATCH v3 1/7] ARM: ARM11 MPCore: pgd_alloc is not preempt safe gdavis at mvista.com
2011-10-07 16:26 ` [RFC/PATCH v3 2/7] ARM: ARM11 MPCore: pte_alloc_one{, _kernel} are " gdavis at mvista.com
2011-10-07 16:26 ` [RFC/PATCH v3 3/7] ARM: ARM11 MPCore: {clean, flush}_pmd_entry " gdavis at mvista.com
2011-10-07 16:26 ` [RFC/PATCH v3 4/7] ARM: ARM11 MPCore: clean_dcache_area is " gdavis at mvista.com
2011-10-07 16:26 ` [RFC/PATCH v3 5/7] ARM: Move get_thread_info macro definition to <asm/assembler.h> gdavis at mvista.com
2011-10-07 16:26 ` [RFC/PATCH v3 6/7] ARM: ARM11 MPCore: DMA_CACHE_RWFO operations are not preempt safe gdavis at mvista.com
2011-10-07 16:26 ` [RFC/PATCH v3 7/7] ARM: ARM11 MPCore: cpu_v6_set_pte_ext is " gdavis at mvista.com
2011-10-18 13:47 ` [RFC/PATCH v4 0/7] ARM11 MPCore: preemption/task migration cache coherency fixups gdavis at mvista.com
2011-10-18 13:47 ` [RFC/PATCH v4 1/7] ARM: ARM11 MPCore: pgd_alloc is not preempt safe gdavis at mvista.com
2011-10-18 13:47 ` [RFC/PATCH v4 2/7] ARM: ARM11 MPCore: pte_alloc_one{, _kernel} are " gdavis at mvista.com
2011-10-18 13:47 ` [RFC/PATCH v4 3/7] ARM: ARM11 MPCore: {clean, flush}_pmd_entry " gdavis at mvista.com
2011-10-18 13:47 ` [RFC/PATCH v4 4/7] ARM: ARM11 MPCore: clean_dcache_area is " gdavis at mvista.com
2011-10-18 17:08 ` Tony Lindgren
2011-10-18 17:30 ` George G. Davis
2011-10-18 17:43 ` Tony Lindgren
2011-10-18 18:13 ` George G. Davis
2011-10-18 13:47 ` [RFC/PATCH v4 5/7] ARM: Move get_thread_info macro definition to <asm/assembler.h> gdavis at mvista.com
2011-10-18 13:47 ` [RFC/PATCH v4 6/7] ARM: ARM11 MPCore: DMA_CACHE_RWFO operations are not preempt safe gdavis at mvista.com
2011-10-18 21:28 ` Nicolas Pitre
2011-10-18 23:26 ` George G. Davis [this message]
2011-10-19 1:09 ` Nicolas Pitre
2011-10-18 13:47 ` [RFC/PATCH v4 7/7] ARM: ARM11 MPCore: cpu_v6_set_pte_ext is " gdavis at mvista.com
2011-10-18 21:52 ` Nicolas Pitre
2011-10-18 23:29 ` George G. Davis
2012-06-12 20:40 ` [RFC/PATCH v5 0/7] ARM11 MPCore: preemption/task migration cache coherency fixups gdavis at mvista.com
2012-06-12 20:40 ` [RFC/PATCH v5 1/7] ARM: ARM11 MPCore: Make pgd_alloc preempt safe gdavis at mvista.com
2012-06-12 20:40 ` [RFC/PATCH v5 2/7] ARM: ARM11 MPCore: Make pte_alloc_one{, _kernel} " gdavis at mvista.com
2012-06-12 20:40 ` [RFC/PATCH v5 3/7] ARM: ARM11 MPCore: Make {clean, flush}_pmd_entry " gdavis at mvista.com
2012-06-12 20:40 ` [RFC/PATCH v5 4/7] ARM: Move get_thread_info macro definition to <asm/assembler.h> gdavis at mvista.com
2012-06-12 20:40 ` [RFC/PATCH v5 5/7] ARM: ARM11 MPCore: cpu_v6_dcache_clean_area needs RFO gdavis at mvista.com
2012-06-13 9:32 ` Catalin Marinas
2012-06-13 9:36 ` Russell King - ARM Linux
2012-06-13 9:41 ` Catalin Marinas
2012-06-13 9:45 ` Russell King - ARM Linux
2012-06-13 9:54 ` Catalin Marinas
2012-06-13 11:36 ` George G. Davis
2012-06-13 11:21 ` George G. Davis
2012-06-12 20:40 ` [RFC/PATCH v5 6/7] ARM: ARM11 MPCore: Make DMA_CACHE_RWFO operations preempt safe gdavis at mvista.com
2012-06-12 20:40 ` [RFC/PATCH v5 7/7] ARM: ARM11 MPCore: Make cpu_v6_set_pte_ext " gdavis at mvista.com
2012-06-13 9:34 ` Catalin Marinas
2012-06-13 11:35 ` George G. Davis
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