On Mon, May 07, 2018 at 01:18:26PM +0200, Simon Horman wrote:
> On Thu, May 03, 2018 at 10:02:18PM +0300, Julian Anastasov wrote:
> > Local clients are not properly synchronized on 32-bit CPUs when
> > updating stats (3.10+). Now it is possible estimation_timer (timer),
> > a stats reader, to interrupt the local client in the middle of
> > write_seqcount_{begin,end} sequence leading to loop (DEADLOCK).
> > The same interrupt can happen from received packet (SoftIRQ)
> > which updates the same per-CPU stats.
> >
> > Fix it by disabling BH while updating stats.
> >
> > Found with debug:
> >
> > WARNING: inconsistent lock state
> > 4.17.0-rc2-00105-g35cb6d7-dirty #2 Not tainted
> > --------------------------------
> > inconsistent {IN-SOFTIRQ-R} -> {SOFTIRQ-ON-W} usage.
> > ftp/2545 [HC0[0]:SC0[0]:HE1:SE1] takes:
> > 86845479 (&syncp->seq#6){+.+-}, at: ip_vs_schedule+0x1c5/0x59e [ip_vs]
> > {IN-SOFTIRQ-R} state was registered at:
> > lock_acquire+0x44/0x5b
> > estimation_timer+0x1b3/0x341 [ip_vs]
> > call_timer_fn+0x54/0xcd
> > run_timer_softirq+0x10c/0x12b
> > __do_softirq+0xc1/0x1a9
> > do_softirq_own_stack+0x1d/0x23
> > irq_exit+0x4a/0x64
> > smp_apic_timer_interrupt+0x63/0x71
> > apic_timer_interrupt+0x3a/0x40
> > default_idle+0xa/0xc
> > arch_cpu_idle+0x9/0xb
> > default_idle_call+0x21/0x23
> > do_idle+0xa0/0x167
> > cpu_startup_entry+0x19/0x1b
> > start_secondary+0x133/0x182
> > startup_32_smp+0x164/0x168
> > irq event stamp: 42213
> >
> > other info that might help us debug this:
> > Possible unsafe locking scenario:
> >
> > CPU0
> > ----
> > lock(&syncp->seq#6);
> > <Interrupt>
> > lock(&syncp->seq#6);
> >
> > *** DEADLOCK ***
> >
> > Fixes: ac69269a45e8 ("ipvs: do not disable bh for long time")
> > Signed-off-by: Julian Anastasov <ja@xxxxxx>
>
> Acked-by: Simon Horman <horms@xxxxxxxxxxxx>
>
> Pablo, can you take this into nf?
Applied, thanks.
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