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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@kernel.org>
Debugged-by: "Ahmed S. Darwish" <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: "Erhard F." <erhard_f@mailbox.org>
Link: https://lkml.kernel.org/r/YEXicy6+9MksdLZh@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2021-03-08 09:38:12 +01:00
parent 50bf8080a9
commit d5b0e0677b
1 changed files with 4 additions and 3 deletions
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7
include/linux/u64_stats_sync.h
View File

@ -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)
{