Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH -next for tip:x86/pti] x86/tlb: drop unneeded local vars in enable_l1d_flush_for_task() | Date | Wed, 30 Sep 2020 20:00:59 +0200 |
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On Wed, Sep 30 2020 at 19:03, Peter Zijlstra wrote: > On Wed, Sep 30, 2020 at 05:40:08PM +0200, Thomas Gleixner wrote: > Also, that preempt_disable() in there doesn't actually do anything. > Worse, preempt_disable(); for_each_cpu(); is an anti-pattern. It mixes > static_cpu_has() and boot_cpu_has() in the same bloody condition and has > a pointless ret variable.
I absolutely agree and I really missed it when looking at it before merging. cpus_read_lock()/unlock() is the right thing to do if at all.
> It's shoddy code, that only works if you align the planets right. We > really shouldn't provide interfaces that are this bad. > > It's correct operation is only by accident.
True :(
I understand Balbirs problem and it makes some sense to provide a solution. We can:
1) reject set_affinity() if the task has that flush muck enabled and user space tries to move it to a SMT enabled core
2) disable the muck if if detects that it is runs on a SMT enabled core suddenly (hotplug says hello)
This one is nasty because there is no feedback to user space about the wreckage.
Thanks,
tglx
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