[PATCH net-next] net: alacritech: Use u64_stats_t with u64_stats_sync properly

[PATCH net-next] net: alacritech: Use u64_stats_t with u64_stats_sync properly

[David Yang]

On 64bit arches, struct u64_stats_sync is empty and provides no help
against load/store tearing. Convert to u64_stats_t to ensure atomic
operations.

Signed-off-by: David Yang <mmyangfl@gmail.com>
---
 drivers/net/ethernet/alacritech/slic.h    | 50 +++++++++++------------
 drivers/net/ethernet/alacritech/slicoss.c |  8 ++--
 2 files changed, 29 insertions(+), 29 deletions(-)

diff --git a/drivers/net/ethernet/alacritech/slic.h b/drivers/net/ethernet/alacritech/slic.h
index 82071d0e5f7f..f5bb2d9a61be 100644
--- a/drivers/net/ethernet/alacritech/slic.h
+++ b/drivers/net/ethernet/alacritech/slic.h
@@ -284,7 +284,7 @@
 #define SLIC_INC_STATS_COUNTER(st, counter)	\
 do {						\
 	u64_stats_update_begin(&(st)->syncp);	\
-	(st)->counter++;			\
+	u64_stats_inc(&(st)->counter);		\
 	u64_stats_update_end(&(st)->syncp);	\
 } while (0)
 
@@ -293,7 +293,7 @@ do {						\
 	unsigned int start;					\
 	do {							\
 		start = u64_stats_fetch_begin(&(st)->syncp);	\
-		newst = (st)->counter;				\
+		newst = u64_stats_read(&(st)->counter);		\
 	} while (u64_stats_fetch_retry(&(st)->syncp, start));	\
 }
 
@@ -407,34 +407,34 @@ struct slic_oasis_eeprom {
 };
 
 struct slic_stats {
-	u64 rx_packets;
-	u64 rx_bytes;
-	u64 rx_mcasts;
-	u64 rx_errors;
-	u64 tx_packets;
-	u64 tx_bytes;
+	u64_stats_t rx_packets;
+	u64_stats_t rx_bytes;
+	u64_stats_t rx_mcasts;
+	u64_stats_t rx_errors;
+	u64_stats_t tx_packets;
+	u64_stats_t tx_bytes;
 	/* HW STATS */
-	u64 rx_buff_miss;
-	u64 tx_dropped;
-	u64 irq_errs;
+	u64_stats_t rx_buff_miss;
+	u64_stats_t tx_dropped;
+	u64_stats_t irq_errs;
 	/* transport layer */
-	u64 rx_tpcsum;
-	u64 rx_tpoflow;
-	u64 rx_tphlen;
+	u64_stats_t rx_tpcsum;
+	u64_stats_t rx_tpoflow;
+	u64_stats_t rx_tphlen;
 	/* ip layer */
-	u64 rx_ipcsum;
-	u64 rx_iplen;
-	u64 rx_iphlen;
+	u64_stats_t rx_ipcsum;
+	u64_stats_t rx_iplen;
+	u64_stats_t rx_iphlen;
 	/* link layer */
-	u64 rx_early;
-	u64 rx_buffoflow;
-	u64 rx_lcode;
-	u64 rx_drbl;
-	u64 rx_crc;
-	u64 rx_oflow802;
-	u64 rx_uflow802;
+	u64_stats_t rx_early;
+	u64_stats_t rx_buffoflow;
+	u64_stats_t rx_lcode;
+	u64_stats_t rx_drbl;
+	u64_stats_t rx_crc;
+	u64_stats_t rx_oflow802;
+	u64_stats_t rx_uflow802;
 	/* oasis only */
-	u64 tx_carrier;
+	u64_stats_t tx_carrier;
 	struct u64_stats_sync syncp;
 };
 
diff --git a/drivers/net/ethernet/alacritech/slicoss.c b/drivers/net/ethernet/alacritech/slicoss.c
index f62851708d4f..7488fb6ace0b 100644
--- a/drivers/net/ethernet/alacritech/slicoss.c
+++ b/drivers/net/ethernet/alacritech/slicoss.c
@@ -378,8 +378,8 @@ static void slic_xmit_complete(struct slic_device *sdev)
 	smp_wmb();
 
 	u64_stats_update_begin(&sdev->stats.syncp);
-	sdev->stats.tx_bytes += bytes;
-	sdev->stats.tx_packets += frames;
+	u64_stats_add(&sdev->stats.tx_bytes, bytes);
+	u64_stats_add(&sdev->stats.tx_packets, frames);
 	u64_stats_update_end(&sdev->stats.syncp);
 
 	netif_tx_lock(dev);
@@ -615,8 +615,8 @@ static void slic_handle_receive(struct slic_device *sdev, unsigned int todo,
 	}
 
 	u64_stats_update_begin(&sdev->stats.syncp);
-	sdev->stats.rx_bytes += bytes;
-	sdev->stats.rx_packets += frames;
+	u64_stats_add(&sdev->stats.rx_bytes, bytes);
+	u64_stats_add(&sdev->stats.rx_packets, frames);
 	u64_stats_update_end(&sdev->stats.syncp);
 
 	slic_refill_rx_queue(sdev, GFP_ATOMIC);
-- 
2.51.0

Re: [PATCH net-next] net: alacritech: Use u64_stats_t with u64_stats_sync properly

[Jakub Kicinski]

On Fri, 23 Jan 2026 02:51:07 +0800 David Yang wrote:
> On 64bit arches, struct u64_stats_sync is empty and provides no help
> against load/store tearing. Convert to u64_stats_t to ensure atomic
> operations.

Eric, could you comment if this matters? I expect David may send a
non-trivial number of these, I want to make sure we're making good
use of everyone's time here. 64b accesses are not torn on 64b arches,
and never used for control flow.

Re: [PATCH net-next] net: alacritech: Use u64_stats_t with u64_stats_sync properly

[Eric Dumazet]

On Mon, Jan 26, 2026 at 12:23 AM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Fri, 23 Jan 2026 02:51:07 +0800 David Yang wrote:
> > On 64bit arches, struct u64_stats_sync is empty and provides no help
> > against load/store tearing. Convert to u64_stats_t to ensure atomic
> > operations.
>
> Eric, could you comment if this matters? I expect David may send a
> non-trivial number of these, I want to make sure we're making good
> use of everyone's time here. 64b accesses are not torn on 64b arches,
> and never used for control flow.

I  added u64_stats_add()/u64_stats_inc() back in 2019, and never bothered
sending dozens of patches.

Presumably compilers could be really dumb back then, I am not sure
this is still the case today.

Re: [PATCH net-next] net: alacritech: Use u64_stats_t with u64_stats_sync properly

[David Laight]

On Mon, 26 Jan 2026 11:11:09 +0100
Eric Dumazet <edumazet@google.com> wrote:

> On Mon, Jan 26, 2026 at 12:23 AM Jakub Kicinski <kuba@kernel.org> wrote:
> >
> > On Fri, 23 Jan 2026 02:51:07 +0800 David Yang wrote:  
> > > On 64bit arches, struct u64_stats_sync is empty and provides no help
> > > against load/store tearing. Convert to u64_stats_t to ensure atomic
> > > operations.  
> >
> > Eric, could you comment if this matters? I expect David may send a
> > non-trivial number of these, I want to make sure we're making good
> > use of everyone's time here. 64b accesses are not torn on 64b arches,
> > and never used for control flow.  
> 
> I  added u64_stats_add()/u64_stats_inc() back in 2019, and never bothered
> sending dozens of patches.
> 
> Presumably compilers could be really dumb back then, I am not sure
> this is still the case today.
> 

gcc still generates 'crap code' for var_64 += var_32 on x86-32.
Basically it zero-extends then does a 64bit add rather than
using 'adc $0, %reg_hi', the extra register is likely to force
a spill to stack.
But that is 'fixed' by using add_u64_u32().

Oh and you really don't want to support adding a signed 32bit value
for one place that wants to do a subtract.

	David

Re: [PATCH net-next] net: alacritech: Use u64_stats_t with u64_stats_sync properly

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 23 Jan 2026 02:51:07 +0800 you wrote:
> On 64bit arches, struct u64_stats_sync is empty and provides no help
> against load/store tearing. Convert to u64_stats_t to ensure atomic
> operations.
> 
> Signed-off-by: David Yang <mmyangfl@gmail.com>
> ---
>  drivers/net/ethernet/alacritech/slic.h    | 50 +++++++++++------------
>  drivers/net/ethernet/alacritech/slicoss.c |  8 ++--
>  2 files changed, 29 insertions(+), 29 deletions(-)

Here is the summary with links:
  - [net-next] net: alacritech: Use u64_stats_t with u64_stats_sync properly
    https://git.kernel.org/netdev/net-next/c/6e9674a980f5

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html