On Fri, Mar 1, 2024 at 10:09 AM Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
>
> On Fri, Mar 1, 2024 at 2:11 AM Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:
> >
> > Hi all,
> >
> > After merging the net-next tree, today's linux-next build (arm
> > multi_v7_defconfig) failed like this:
> >
> > In file included from <command-line>:
> > In function 'tcp_struct_check',
> > inlined from 'tcp_init' at net/ipv4/tcp.c:4700:2:
> > include/linux/compiler_types.h:442:45: error: call to '__compiletime_assert_940' declared with attribute error: BUILD_BUG_ON failed: offsetof(struct tcp_sock, __cacheline_group_end__tcp_sock_write_rx) - offsetofend(struct tcp_sock, __cacheline_group_begin__tcp_sock_write_rx) > 99
> > 442 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > | ^
> > include/linux/compiler_types.h:423:25: note: in definition of macro '__compiletime_assert'
> > 423 | prefix ## suffix(); \
> > | ^~~~~~
> > include/linux/compiler_types.h:442:9: note: in expansion of macro '_compiletime_assert'
> > 442 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > | ^~~~~~~~~~~~~~~~~~~
> > include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
> > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> > | ^~~~~~~~~~~~~~~~~~
> > include/linux/build_bug.h:50:9: note: in expansion of macro 'BUILD_BUG_ON_MSG'
> > 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
> > | ^~~~~~~~~~~~~~~~
> > include/linux/cache.h:108:9: note: in expansion of macro 'BUILD_BUG_ON'
> > 108 | BUILD_BUG_ON(offsetof(TYPE, __cacheline_group_end__##GROUP) - \
> > | ^~~~~~~~~~~~
> > net/ipv4/tcp.c:4687:9: note: in expansion of macro 'CACHELINE_ASSERT_GROUP_SIZE'
> > 4687 | CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_write_rx, 99);
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Caused by commit
> >
> > 99123622050f ("tcp: remove some holes in struct tcp_sock")
> >
> > I have reverted that commit for today.
> >
>
> I have no idea. Maybe this arch has some unusual alignments on
> u64/u32/u16 fields ?
>
> The patch should not have changed tcp_sock_write_rx group...
>
> My patch reduced tcp_sock_write_tx on x86_64 from 113 to 105 bytes but
> I did not bother changing the assert,
> because the assertion triggers if the size of the group is bigger than
> the numerical value.
>
OK, I think the issue is caused by a hole at the start of
tcp_sock_write_rx group
I will send this patch for review, thanks !
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 988a30ef6bfe956fa573f1f18c8284aa382dc1cc..55399ee2a57e736b55ed067fc06ea620bbe62fd3
100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -304,7 +304,7 @@ struct tcp_sock {
__cacheline_group_end(tcp_sock_write_txrx);
/* RX read-write hotpath cache lines */
- __cacheline_group_begin(tcp_sock_write_rx);
+ __cacheline_group_begin(tcp_sock_write_rx) __aligned(8);
u64 bytes_received;
/* RFC4898 tcpEStatsAppHCThruOctetsReceived
* sum(delta(rcv_nxt)), or how many bytes
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c82dc42f57c65df112f79080ff407cd98d11ce68..7e1b848398d04f2da2a91c3af97b1e2e3895b8ee
100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4651,7 +4651,7 @@ static void __init tcp_struct_check(void)
CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock,
tcp_sock_write_tx, tsorted_sent_queue);
CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock,
tcp_sock_write_tx, highest_sack);
CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock,
tcp_sock_write_tx, ecn_flags);
- CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_write_tx, 113);
+ CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_write_tx, 105);
/* TXRX read-write hotpath cache lines */
CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock,
tcp_sock_write_txrx, pred_flags);
