* [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-22 20:03 ` Iyappan Subramanian
0 siblings, 0 replies; 15+ messages in thread
From: Iyappan Subramanian @ 2015-01-22 20:03 UTC (permalink / raw)
To: davem, netdev
Cc: linux-kernel, linux-arm-kernel, mlangsdo, patches,
Iyappan Subramanian, Keyur Chudgar
This patch fixes the following kernel crash,
WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
Call trace:
[<fffffe0000096b7c>] dump_backtrace+0x0/0x184
[<fffffe0000096d10>] show_stack+0x10/0x1c
[<fffffe0000685ea0>] dump_stack+0x74/0x98
[<fffffe00000b44e0>] warn_slowpath_common+0x88/0xb0
[<fffffe00000b461c>] warn_slowpath_null+0x14/0x20
[<fffffe00005b5c1c>] tcp_clean_rtx_queue+0x654/0x80c
[<fffffe00005b6228>] tcp_ack+0x454/0x688
[<fffffe00005b6ca8>] tcp_rcv_established+0x4a4/0x62c
[<fffffe00005bf4b4>] tcp_v4_do_rcv+0x16c/0x350
[<fffffe00005c225c>] tcp_v4_rcv+0x8e8/0x904
[<fffffe000059d470>] ip_local_deliver_finish+0x100/0x26c
[<fffffe000059dad8>] ip_local_deliver+0xac/0xc4
[<fffffe000059d6c4>] ip_rcv_finish+0xe8/0x328
[<fffffe000059dd3c>] ip_rcv+0x24c/0x38c
[<fffffe0000563950>] __netif_receive_skb_core+0x29c/0x7c8
[<fffffe0000563ea4>] __netif_receive_skb+0x28/0x7c
[<fffffe0000563f54>] netif_receive_skb_internal+0x5c/0xe0
[<fffffe0000564810>] napi_gro_receive+0xb4/0x110
[<fffffe0000482a2c>] xgene_enet_process_ring+0x144/0x338
[<fffffe0000482d18>] xgene_enet_napi+0x1c/0x50
[<fffffe0000565454>] net_rx_action+0x154/0x228
[<fffffe00000b804c>] __do_softirq+0x110/0x28c
[<fffffe00000b8424>] irq_exit+0x8c/0xc0
[<fffffe0000093898>] handle_IRQ+0x44/0xa8
[<fffffe000009032c>] gic_handle_irq+0x38/0x7c
[...]
Software writes poison data into the descriptor bytes[15:8] and upon
receiving the interrupt, if those bytes are overwritten by the hardware with
the valid data, software also reads bytes[7:0] and executes receive/tx
completion logic.
If the CPU executes the above two reads in out of order fashion, then the
bytes[7:0] will have older data and causing the kernel panic. We have to
force the order of the reads and thus this patch introduces read memory
barrier between these reads.
Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
---
drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
index 83a5028..3622cdb 100644
--- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
+++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
@@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
break;
+ /* read fpqnum field after dataaddr field */
+ smp_rmb();
if (is_rx_desc(raw_desc))
ret = xgene_enet_rx_frame(ring, raw_desc);
else
--
1.9.1
^ permalink raw reply related [flat|nested] 15+ messages in thread
* [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-22 20:03 ` Iyappan Subramanian
0 siblings, 0 replies; 15+ messages in thread
From: Iyappan Subramanian @ 2015-01-22 20:03 UTC (permalink / raw)
To: linux-arm-kernel
This patch fixes the following kernel crash,
WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
Call trace:
[<fffffe0000096b7c>] dump_backtrace+0x0/0x184
[<fffffe0000096d10>] show_stack+0x10/0x1c
[<fffffe0000685ea0>] dump_stack+0x74/0x98
[<fffffe00000b44e0>] warn_slowpath_common+0x88/0xb0
[<fffffe00000b461c>] warn_slowpath_null+0x14/0x20
[<fffffe00005b5c1c>] tcp_clean_rtx_queue+0x654/0x80c
[<fffffe00005b6228>] tcp_ack+0x454/0x688
[<fffffe00005b6ca8>] tcp_rcv_established+0x4a4/0x62c
[<fffffe00005bf4b4>] tcp_v4_do_rcv+0x16c/0x350
[<fffffe00005c225c>] tcp_v4_rcv+0x8e8/0x904
[<fffffe000059d470>] ip_local_deliver_finish+0x100/0x26c
[<fffffe000059dad8>] ip_local_deliver+0xac/0xc4
[<fffffe000059d6c4>] ip_rcv_finish+0xe8/0x328
[<fffffe000059dd3c>] ip_rcv+0x24c/0x38c
[<fffffe0000563950>] __netif_receive_skb_core+0x29c/0x7c8
[<fffffe0000563ea4>] __netif_receive_skb+0x28/0x7c
[<fffffe0000563f54>] netif_receive_skb_internal+0x5c/0xe0
[<fffffe0000564810>] napi_gro_receive+0xb4/0x110
[<fffffe0000482a2c>] xgene_enet_process_ring+0x144/0x338
[<fffffe0000482d18>] xgene_enet_napi+0x1c/0x50
[<fffffe0000565454>] net_rx_action+0x154/0x228
[<fffffe00000b804c>] __do_softirq+0x110/0x28c
[<fffffe00000b8424>] irq_exit+0x8c/0xc0
[<fffffe0000093898>] handle_IRQ+0x44/0xa8
[<fffffe000009032c>] gic_handle_irq+0x38/0x7c
[...]
Software writes poison data into the descriptor bytes[15:8] and upon
receiving the interrupt, if those bytes are overwritten by the hardware with
the valid data, software also reads bytes[7:0] and executes receive/tx
completion logic.
If the CPU executes the above two reads in out of order fashion, then the
bytes[7:0] will have older data and causing the kernel panic. We have to
force the order of the reads and thus this patch introduces read memory
barrier between these reads.
Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
---
drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
index 83a5028..3622cdb 100644
--- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
+++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
@@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
break;
+ /* read fpqnum field after dataaddr field */
+ smp_rmb();
if (is_rx_desc(raw_desc))
ret = xgene_enet_rx_frame(ring, raw_desc);
else
--
1.9.1
^ permalink raw reply related [flat|nested] 15+ messages in thread
* Re: [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
2015-01-22 20:03 ` Iyappan Subramanian
@ 2015-01-22 22:50 ` Eric Dumazet
-1 siblings, 0 replies; 15+ messages in thread
From: Eric Dumazet @ 2015-01-22 22:50 UTC (permalink / raw)
To: Iyappan Subramanian
Cc: davem, netdev, linux-kernel, linux-arm-kernel, mlangsdo, patches,
Keyur Chudgar
On Thu, 2015-01-22 at 12:03 -0800, Iyappan Subramanian wrote:
> This patch fixes the following kernel crash,
>
> WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
> Call trace:
>
> Software writes poison data into the descriptor bytes[15:8] and upon
> receiving the interrupt, if those bytes are overwritten by the hardware with
> the valid data, software also reads bytes[7:0] and executes receive/tx
> completion logic.
>
> If the CPU executes the above two reads in out of order fashion, then the
> bytes[7:0] will have older data and causing the kernel panic. We have to
> force the order of the reads and thus this patch introduces read memory
> barrier between these reads.
>
> Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
> Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
> Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
> ---
> drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> index 83a5028..3622cdb 100644
> --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
> break;
>
> + /* read fpqnum field after dataaddr field */
> + smp_rmb();
> if (is_rx_desc(raw_desc))
> ret = xgene_enet_rx_frame(ring, raw_desc);
> else
Reading your changelog, it looks like you need a plain rmb() here.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-22 22:50 ` Eric Dumazet
0 siblings, 0 replies; 15+ messages in thread
From: Eric Dumazet @ 2015-01-22 22:50 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, 2015-01-22 at 12:03 -0800, Iyappan Subramanian wrote:
> This patch fixes the following kernel crash,
>
> WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
> Call trace:
>
> Software writes poison data into the descriptor bytes[15:8] and upon
> receiving the interrupt, if those bytes are overwritten by the hardware with
> the valid data, software also reads bytes[7:0] and executes receive/tx
> completion logic.
>
> If the CPU executes the above two reads in out of order fashion, then the
> bytes[7:0] will have older data and causing the kernel panic. We have to
> force the order of the reads and thus this patch introduces read memory
> barrier between these reads.
>
> Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
> Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
> Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
> ---
> drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> index 83a5028..3622cdb 100644
> --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
> break;
>
> + /* read fpqnum field after dataaddr field */
> + smp_rmb();
> if (is_rx_desc(raw_desc))
> ret = xgene_enet_rx_frame(ring, raw_desc);
> else
Reading your changelog, it looks like you need a plain rmb() here.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
2015-01-22 22:50 ` Eric Dumazet
(?)
@ 2015-01-26 21:12 ` Iyappan Subramanian
-1 siblings, 0 replies; 15+ messages in thread
From: Iyappan Subramanian @ 2015-01-26 21:12 UTC (permalink / raw)
To: Eric Dumazet
Cc: David Miller, netdev, linux-kernel, linux-arm-kernel, mlangsdo,
patches, Keyur Chudgar
On Thu, Jan 22, 2015 at 2:50 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Thu, 2015-01-22 at 12:03 -0800, Iyappan Subramanian wrote:
>> This patch fixes the following kernel crash,
>>
>> WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
>> Call trace:
>
>>
>> Software writes poison data into the descriptor bytes[15:8] and upon
>> receiving the interrupt, if those bytes are overwritten by the hardware with
>> the valid data, software also reads bytes[7:0] and executes receive/tx
>> completion logic.
>>
>> If the CPU executes the above two reads in out of order fashion, then the
>> bytes[7:0] will have older data and causing the kernel panic. We have to
>> force the order of the reads and thus this patch introduces read memory
>> barrier between these reads.
>>
>> Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
>> Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
>> Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
>> ---
>> drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
>> index 83a5028..3622cdb 100644
>> --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
>> +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
>> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
>> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
>> break;
>>
>> + /* read fpqnum field after dataaddr field */
>> + smp_rmb();
>> if (is_rx_desc(raw_desc))
>> ret = xgene_enet_rx_frame(ring, raw_desc);
>> else
>
> Reading your changelog, it looks like you need a plain rmb() here.
rmb() translates into dsb, which in arm64 serializes everything
including instructions and thus expensive compared to dmb.
Do you see any issue with smp_rmb() (which translates into dmb) ?
>
>
>
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-26 21:12 ` Iyappan Subramanian
0 siblings, 0 replies; 15+ messages in thread
From: Iyappan Subramanian @ 2015-01-26 21:12 UTC (permalink / raw)
To: Eric Dumazet
Cc: David Miller, netdev, linux-kernel, linux-arm-kernel, mlangsdo,
patches, Keyur Chudgar
On Thu, Jan 22, 2015 at 2:50 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Thu, 2015-01-22 at 12:03 -0800, Iyappan Subramanian wrote:
>> This patch fixes the following kernel crash,
>>
>> WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
>> Call trace:
>
>>
>> Software writes poison data into the descriptor bytes[15:8] and upon
>> receiving the interrupt, if those bytes are overwritten by the hardware with
>> the valid data, software also reads bytes[7:0] and executes receive/tx
>> completion logic.
>>
>> If the CPU executes the above two reads in out of order fashion, then the
>> bytes[7:0] will have older data and causing the kernel panic. We have to
>> force the order of the reads and thus this patch introduces read memory
>> barrier between these reads.
>>
>> Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
>> Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
>> Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
>> ---
>> drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
>> index 83a5028..3622cdb 100644
>> --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
>> +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
>> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
>> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
>> break;
>>
>> + /* read fpqnum field after dataaddr field */
>> + smp_rmb();
>> if (is_rx_desc(raw_desc))
>> ret = xgene_enet_rx_frame(ring, raw_desc);
>> else
>
> Reading your changelog, it looks like you need a plain rmb() here.
rmb() translates into dsb, which in arm64 serializes everything
including instructions and thus expensive compared to dmb.
Do you see any issue with smp_rmb() (which translates into dmb) ?
>
>
>
^ permalink raw reply [flat|nested] 15+ messages in thread
* [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-26 21:12 ` Iyappan Subramanian
0 siblings, 0 replies; 15+ messages in thread
From: Iyappan Subramanian @ 2015-01-26 21:12 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jan 22, 2015 at 2:50 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Thu, 2015-01-22 at 12:03 -0800, Iyappan Subramanian wrote:
>> This patch fixes the following kernel crash,
>>
>> WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
>> Call trace:
>
>>
>> Software writes poison data into the descriptor bytes[15:8] and upon
>> receiving the interrupt, if those bytes are overwritten by the hardware with
>> the valid data, software also reads bytes[7:0] and executes receive/tx
>> completion logic.
>>
>> If the CPU executes the above two reads in out of order fashion, then the
>> bytes[7:0] will have older data and causing the kernel panic. We have to
>> force the order of the reads and thus this patch introduces read memory
>> barrier between these reads.
>>
>> Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
>> Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
>> Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
>> ---
>> drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
>> index 83a5028..3622cdb 100644
>> --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
>> +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
>> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
>> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
>> break;
>>
>> + /* read fpqnum field after dataaddr field */
>> + smp_rmb();
>> if (is_rx_desc(raw_desc))
>> ret = xgene_enet_rx_frame(ring, raw_desc);
>> else
>
> Reading your changelog, it looks like you need a plain rmb() here.
rmb() translates into dsb, which in arm64 serializes everything
including instructions and thus expensive compared to dmb.
Do you see any issue with smp_rmb() (which translates into dmb) ?
>
>
>
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
2015-01-26 21:12 ` Iyappan Subramanian
(?)
@ 2015-01-26 21:27 ` Eric Dumazet
-1 siblings, 0 replies; 15+ messages in thread
From: Eric Dumazet @ 2015-01-26 21:27 UTC (permalink / raw)
To: Iyappan Subramanian
Cc: David Miller, netdev, linux-kernel, linux-arm-kernel, mlangsdo,
patches, Keyur Chudgar
On Mon, 2015-01-26 at 13:12 -0800, Iyappan Subramanian wrote:
> On Thu, Jan 22, 2015 at 2:50 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > On Thu, 2015-01-22 at 12:03 -0800, Iyappan Subramanian wrote:
> >> This patch fixes the following kernel crash,
> >>
> >> WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
> >> Call trace:
> >
> >>
> >> Software writes poison data into the descriptor bytes[15:8] and upon
> >> receiving the interrupt, if those bytes are overwritten by the hardware with
> >> the valid data, software also reads bytes[7:0] and executes receive/tx
> >> completion logic.
> >>
> >> If the CPU executes the above two reads in out of order fashion, then the
> >> bytes[7:0] will have older data and causing the kernel panic. We have to
> >> force the order of the reads and thus this patch introduces read memory
> >> barrier between these reads.
> >>
> >> Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
> >> Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
> >> Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
> >> ---
> >> drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
> >> 1 file changed, 2 insertions(+)
> >>
> >> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >> index 83a5028..3622cdb 100644
> >> --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >> +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
> >> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
> >> break;
> >>
> >> + /* read fpqnum field after dataaddr field */
> >> + smp_rmb();
> >> if (is_rx_desc(raw_desc))
> >> ret = xgene_enet_rx_frame(ring, raw_desc);
> >> else
> >
> > Reading your changelog, it looks like you need a plain rmb() here.
>
> rmb() translates into dsb, which in arm64 serializes everything
> including instructions and thus expensive compared to dmb.
>
> Do you see any issue with smp_rmb() (which translates into dmb) ?
What happens if you compile a kernel with CONFIG_SMP=n ?
Most drivers in drivers/net use rmb() in this case, not smp_rmb() or
barrier()
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-26 21:27 ` Eric Dumazet
0 siblings, 0 replies; 15+ messages in thread
From: Eric Dumazet @ 2015-01-26 21:27 UTC (permalink / raw)
To: Iyappan Subramanian
Cc: David Miller, netdev, linux-kernel, linux-arm-kernel, mlangsdo,
patches, Keyur Chudgar
On Mon, 2015-01-26 at 13:12 -0800, Iyappan Subramanian wrote:
> On Thu, Jan 22, 2015 at 2:50 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > On Thu, 2015-01-22 at 12:03 -0800, Iyappan Subramanian wrote:
> >> This patch fixes the following kernel crash,
> >>
> >> WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
> >> Call trace:
> >
> >>
> >> Software writes poison data into the descriptor bytes[15:8] and upon
> >> receiving the interrupt, if those bytes are overwritten by the hardware with
> >> the valid data, software also reads bytes[7:0] and executes receive/tx
> >> completion logic.
> >>
> >> If the CPU executes the above two reads in out of order fashion, then the
> >> bytes[7:0] will have older data and causing the kernel panic. We have to
> >> force the order of the reads and thus this patch introduces read memory
> >> barrier between these reads.
> >>
> >> Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
> >> Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
> >> Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
> >> ---
> >> drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
> >> 1 file changed, 2 insertions(+)
> >>
> >> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >> index 83a5028..3622cdb 100644
> >> --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >> +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
> >> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
> >> break;
> >>
> >> + /* read fpqnum field after dataaddr field */
> >> + smp_rmb();
> >> if (is_rx_desc(raw_desc))
> >> ret = xgene_enet_rx_frame(ring, raw_desc);
> >> else
> >
> > Reading your changelog, it looks like you need a plain rmb() here.
>
> rmb() translates into dsb, which in arm64 serializes everything
> including instructions and thus expensive compared to dmb.
>
> Do you see any issue with smp_rmb() (which translates into dmb) ?
What happens if you compile a kernel with CONFIG_SMP=n ?
Most drivers in drivers/net use rmb() in this case, not smp_rmb() or
barrier()
^ permalink raw reply [flat|nested] 15+ messages in thread
* [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-26 21:27 ` Eric Dumazet
0 siblings, 0 replies; 15+ messages in thread
From: Eric Dumazet @ 2015-01-26 21:27 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, 2015-01-26 at 13:12 -0800, Iyappan Subramanian wrote:
> On Thu, Jan 22, 2015 at 2:50 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > On Thu, 2015-01-22 at 12:03 -0800, Iyappan Subramanian wrote:
> >> This patch fixes the following kernel crash,
> >>
> >> WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c()
> >> Call trace:
> >
> >>
> >> Software writes poison data into the descriptor bytes[15:8] and upon
> >> receiving the interrupt, if those bytes are overwritten by the hardware with
> >> the valid data, software also reads bytes[7:0] and executes receive/tx
> >> completion logic.
> >>
> >> If the CPU executes the above two reads in out of order fashion, then the
> >> bytes[7:0] will have older data and causing the kernel panic. We have to
> >> force the order of the reads and thus this patch introduces read memory
> >> barrier between these reads.
> >>
> >> Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
> >> Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
> >> Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
> >> ---
> >> drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 2 ++
> >> 1 file changed, 2 insertions(+)
> >>
> >> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >> index 83a5028..3622cdb 100644
> >> --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >> +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
> >> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
> >> break;
> >>
> >> + /* read fpqnum field after dataaddr field */
> >> + smp_rmb();
> >> if (is_rx_desc(raw_desc))
> >> ret = xgene_enet_rx_frame(ring, raw_desc);
> >> else
> >
> > Reading your changelog, it looks like you need a plain rmb() here.
>
> rmb() translates into dsb, which in arm64 serializes everything
> including instructions and thus expensive compared to dmb.
>
> Do you see any issue with smp_rmb() (which translates into dmb) ?
What happens if you compile a kernel with CONFIG_SMP=n ?
Most drivers in drivers/net use rmb() in this case, not smp_rmb() or
barrier()
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
2015-01-26 21:27 ` Eric Dumazet
(?)
@ 2015-01-26 21:32 ` Eric Dumazet
-1 siblings, 0 replies; 15+ messages in thread
From: Eric Dumazet @ 2015-01-26 21:32 UTC (permalink / raw)
To: Iyappan Subramanian
Cc: David Miller, netdev, linux-kernel, linux-arm-kernel, mlangsdo,
patches, Keyur Chudgar
On Mon, 2015-01-26 at 13:27 -0800, Eric Dumazet wrote:
> What happens if you compile a kernel with CONFIG_SMP=n ?
>
>
> Most drivers in drivers/net use rmb() in this case, not smp_rmb() or
> barrier()
Note that dma_rmb() was recently added as well.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-26 21:32 ` Eric Dumazet
0 siblings, 0 replies; 15+ messages in thread
From: Eric Dumazet @ 2015-01-26 21:32 UTC (permalink / raw)
To: Iyappan Subramanian
Cc: David Miller, netdev, linux-kernel, linux-arm-kernel, mlangsdo,
patches, Keyur Chudgar
On Mon, 2015-01-26 at 13:27 -0800, Eric Dumazet wrote:
> What happens if you compile a kernel with CONFIG_SMP=n ?
>
>
> Most drivers in drivers/net use rmb() in this case, not smp_rmb() or
> barrier()
Note that dma_rmb() was recently added as well.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-26 21:32 ` Eric Dumazet
0 siblings, 0 replies; 15+ messages in thread
From: Eric Dumazet @ 2015-01-26 21:32 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, 2015-01-26 at 13:27 -0800, Eric Dumazet wrote:
> What happens if you compile a kernel with CONFIG_SMP=n ?
>
>
> Most drivers in drivers/net use rmb() in this case, not smp_rmb() or
> barrier()
Note that dma_rmb() was recently added as well.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
2015-01-26 21:12 ` Iyappan Subramanian
@ 2015-01-26 22:34 ` David Miller
-1 siblings, 0 replies; 15+ messages in thread
From: David Miller @ 2015-01-26 22:34 UTC (permalink / raw)
To: isubramanian
Cc: eric.dumazet, netdev, linux-kernel, linux-arm-kernel, mlangsdo,
patches, kchudgar
From: Iyappan Subramanian <isubramanian@apm.com>
Date: Mon, 26 Jan 2015 13:12:23 -0800
>>> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
>>> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
>>> break;
>>>
>>> + /* read fpqnum field after dataaddr field */
>>> + smp_rmb();
>>> if (is_rx_desc(raw_desc))
>>> ret = xgene_enet_rx_frame(ring, raw_desc);
>>> else
>>
>> Reading your changelog, it looks like you need a plain rmb() here.
>
> rmb() translates into dsb, which in arm64 serializes everything
> including instructions and thus expensive compared to dmb.
>
> Do you see any issue with smp_rmb() (which translates into dmb) ?
smp_rmb() is not appropriate. You're not serializing accesses between
two cpus, you're serializing the cpu with the device.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read
@ 2015-01-26 22:34 ` David Miller
0 siblings, 0 replies; 15+ messages in thread
From: David Miller @ 2015-01-26 22:34 UTC (permalink / raw)
To: linux-arm-kernel
From: Iyappan Subramanian <isubramanian@apm.com>
Date: Mon, 26 Jan 2015 13:12:23 -0800
>>> @@ -369,6 +369,8 @@ static int xgene_enet_process_ring(struct xgene_enet_desc_ring *ring,
>>> if (unlikely(xgene_enet_is_desc_slot_empty(raw_desc)))
>>> break;
>>>
>>> + /* read fpqnum field after dataaddr field */
>>> + smp_rmb();
>>> if (is_rx_desc(raw_desc))
>>> ret = xgene_enet_rx_frame(ring, raw_desc);
>>> else
>>
>> Reading your changelog, it looks like you need a plain rmb() here.
>
> rmb() translates into dsb, which in arm64 serializes everything
> including instructions and thus expensive compared to dmb.
>
> Do you see any issue with smp_rmb() (which translates into dmb) ?
smp_rmb() is not appropriate. You're not serializing accesses between
two cpus, you're serializing the cpu with the device.
^ permalink raw reply [flat|nested] 15+ messages in thread
end of thread, other threads:[~2015-01-26 22:34 UTC | newest]
Thread overview: 15+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-01-22 20:03 [PATCH] drivers: net: xgene: fix: Out of order descriptor bytes read Iyappan Subramanian
2015-01-22 20:03 ` Iyappan Subramanian
2015-01-22 22:50 ` Eric Dumazet
2015-01-22 22:50 ` Eric Dumazet
2015-01-26 21:12 ` Iyappan Subramanian
2015-01-26 21:12 ` Iyappan Subramanian
2015-01-26 21:12 ` Iyappan Subramanian
2015-01-26 21:27 ` Eric Dumazet
2015-01-26 21:27 ` Eric Dumazet
2015-01-26 21:27 ` Eric Dumazet
2015-01-26 21:32 ` Eric Dumazet
2015-01-26 21:32 ` Eric Dumazet
2015-01-26 21:32 ` Eric Dumazet
2015-01-26 22:34 ` David Miller
2015-01-26 22:34 ` David Miller
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.