Messages in this thread | | | Date | Tue, 10 Jan 2023 13:12:09 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH v13 1/6] mm/vmstat: Add CPU-specific variable to track a vmstat discrepancy |
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On Tue, Jan 10, 2023 at 12:58:32PM +0100, Christoph Lameter wrote: > On Thu, 5 Jan 2023, Marcelo Tosatti wrote: > > > +static inline void vmstat_mark_dirty(void) > > +{ > > + this_cpu_write(vmstat_dirty, true); > > +} > > this_cpu_write() is intended for an per cpu atomic context. You are not > using it in that way. The processor may have changed before or after and > thus vmstat_dirty for another CPU may have been marked dirty. > > I guess this would have to be called __vmstat_mark_dirty() and be using > __this_cpu_write(*) with a requirement that preemption be disabled before > using this function.
You're right. So this patchset also arranges for these vmstat functions to be called with preemption disabled. I'm converting the this_cpu operations to __this_cpu versions to make sure of that. And I believe the __this_cpu WARN if preemptible().
> > > +static inline void vmstat_clear_dirty(void) > > +{ > > + this_cpu_write(vmstat_dirty, false); > > +} > > Same > > > +static inline bool is_vmstat_dirty(void) > > +{ > > + return this_cpu_read(vmstat_dirty); > > +} > > This function would only work correctly if preemption is disabled. > Otherwise the processor may change.
Indeed that should apply as __this_cpu_read() as well.
Thanks!
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