nter false positive reports in
> > W+X checking, and the rcu synchronization is unnecessary which can
> > introduce significant delay.
> >
> > Eric Chanudet reports that the rcu_barrier introduces ~0.1s delay on a
> > PREEMPT_RT kernel.
> > [0.291444] Freeing unused
u_preempt
LastCB cpu -1 remaining 0 # 1
systemd-1 [002] . 0.413351: rcu_barrier: rcu_preempt
Inc2 cpu -1 remaining 0 # 1
With this patch the delay is no longer there:
[0.377662] Freeing unused kernel memory: 14080K
[ 0.377767] Run /sbin/init as init process
AFAIU, for the race to happen, module_alloc() needs to create a W+X
mapping (neither x86 nor arm64 does) and debug_checkwx() has to happen
before module_enable_nx() in complete_formation(), I didn't get a
reproducer so far.
Best,
--
Eric Chanudet
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