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SubjectRe: [RFC, PATCH] avoid some atomics in open()/close() for monothreaded processes
Eric Dumazet <dada1@cosmosbay.com> wrote:
>
> Goal : Avoid some locking/unlocking 'struct files_struct'->file_lock for mono
> threaded processes.
>
> We define files_multithreaded() function .
>
> static inline int files_multithreaded(const struct files_struct *files)
> {
> return sizeof(files->file_lock) > 0 && atomic_read(&files->count) > 1;
> }

That's bascially sizeof(spinlock_t). That's architecture dependent and
varies wildly according to the day of week.

It _might_ work in all situations - probably you checked that. But I still
wouldn't do it because it might break in the future. Let's be explicit and
stick the appropriate ifdefs in there.

I'd also consider renaming it to files_shared() - processes are
multithreaded, not data structures.

Once you're done with that we should change fget_light() and fput_light() to
use this helper. Separate patch.

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