The following commit has been merged into the locking/urgent branch of tip:
Commit-ID: d5b0e0677bfd5efd17c5bbb00156931f0d41cb85
Gitweb: https://git.kernel.org/tip/d5b0e0677bfd5efd17c5bbb00156931f0d41cb85
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 08 Mar 2021 09:38:12 +01:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 10 Mar 2021 09:51:45 +01:00
u64_stats,lockdep: Fix u64_stats_init() vs lockdep
Jakub reported that:
static struct net_device *rtl8139_init_board(struct pci_dev *pdev)
{
...
u64_stats_init(&tp->rx_stats.syncp);
u64_stats_init(&tp->tx_stats.syncp);
...
}
results in lockdep getting confused between the RX and TX stats lock.
This is because u64_stats_init() is an inline calling seqcount_init(),
which is a macro using a static variable to generate a lockdep class.
By wrapping that in an inline, we negate the effect of the macro and
fold the static key variable, hence the confusion.
Fix by also making u64_stats_init() a macro for the case where it
matters, leaving the other case an inline for argument validation
etc.
Reported-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Debugged-by: "Ahmed S. Darwish" <a.darwish@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: "Erhard F." <erhard_f@xxxxxxxxxxx>
Link: https://lkml.kernel.org/r/YEXicy6+9MksdLZh@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
---
include/linux/u64_stats_sync.h | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index c6abb79..e81856c 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -115,12 +115,13 @@ static inline void u64_stats_inc(u64_stats_t *p)
}
#endif
+#if BITS_PER_LONG == 32 && defined(CONFIG_SMP)
+#define u64_stats_init(syncp) seqcount_init(&(syncp)->seq)
+#else
static inline void u64_stats_init(struct u64_stats_sync *syncp)
{
-#if BITS_PER_LONG == 32 && defined(CONFIG_SMP)
- seqcount_init(&syncp->seq);
-#endif
}
+#endif
static inline void u64_stats_update_begin(struct u64_stats_sync *syncp)
{
|