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From: Peter Zijlstra <peterz@infradead.org>
To: Roman Penyaev <rpenyaev@suse.de>
Cc: azat@libevent.org, akpm@linux-foundation.org,
	viro@zeniv.linux.org.uk, torvalds@linux-foundation.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 06/13] epoll: introduce helpers for adding/removing events to uring
Date: Fri, 31 May 2019 15:11:27 +0200
Message-ID: <20190531131127.GB2606@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <7187263bcee61b9abbe687f3a7478bd1@suse.de>

On Fri, May 31, 2019 at 01:24:07PM +0200, Roman Penyaev wrote:
> On 2019-05-31 11:55, Peter Zijlstra wrote:
> > On Thu, May 16, 2019 at 10:58:03AM +0200, Roman Penyaev wrote:
> > > +#define atomic_set_unless_zero(ptr, flags)			\
> > > +({								\
> > > +	typeof(ptr) _ptr = (ptr);				\
> > > +	typeof(flags) _flags = (flags);				\
> > > +	typeof(*_ptr) _old, _val = READ_ONCE(*_ptr);		\
> > > +								\
> > > +	for (;;) {						\
> > > +		if (!_val)					\
> > > +			break;					\
> > > +		_old = cmpxchg(_ptr, _val, _flags);		\
> > > +		if (_old == _val)				\
> > > +			break;					\
> > > +		_val = _old;					\
> > > +	}							\
> > > +	_val;							\
> > > +})
> > 
> > > +#define atomic_or_with_mask(ptr, flags, mask)			\
> > > +({								\
> > > +	typeof(ptr) _ptr = (ptr);				\
> > > +	typeof(flags) _flags = (flags);				\
> > > +	typeof(flags) _mask = (mask);				\
> > > +	typeof(*_ptr) _old, _new, _val = READ_ONCE(*_ptr);	\
> > > +								\
> > > +	for (;;) {						\
> > > +		_new = (_val & ~_mask) | _flags;		\
> > > +		_old = cmpxchg(_ptr, _val, _new);		\
> > > +		if (_old == _val)				\
> > > +			break;					\
> > > +		_val = _old;					\
> > > +	}							\
> > > +	_val;							\
> > > +})
> > 
> > Don't call them atomic_*() if they're not part of the atomic_t
> > interface.
> 
> Can we add those two?  Or keep it local is better?

Afaict you're using them on the user visible values; we should not put
atomic_t into shared memory.

Your interface isn't compatible with those 'funny' architectures like
parisc etc. Since you expect userspace to do atomic ops on these
variables too. It is not a one-way interface ...

  reply index

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-16  8:57 [PATCH v3 00/13] epoll: support pollable epoll from userspace Roman Penyaev
2019-05-16  8:57 ` [PATCH v3 01/13] epoll: move private helpers from a header to the source Roman Penyaev
2019-05-16  8:57 ` [PATCH v3 02/13] epoll: introduce user structures for polling from userspace Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 03/13] epoll: allocate user header and user events ring " Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 04/13] epoll: some sanity flags checks for epoll syscalls " Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 05/13] epoll: offload polling to a work in case of epfd polled " Roman Penyaev
2019-05-21  7:51   ` Eric Wong
2019-05-22 12:54     ` Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 06/13] epoll: introduce helpers for adding/removing events to uring Roman Penyaev
2019-05-31  9:55   ` Peter Zijlstra
2019-05-31 11:24     ` Roman Penyaev
2019-05-31 13:11       ` Peter Zijlstra [this message]
2019-05-31  9:56   ` Peter Zijlstra
2019-05-31 11:15     ` Roman Penyaev
2019-05-31 12:53       ` Peter Zijlstra
2019-05-31 14:28         ` Roman Penyaev
2019-05-31 16:53           ` Peter Zijlstra
2019-05-31 12:56       ` Peter Zijlstra
2019-05-31 14:21         ` Roman Penyaev
2019-05-31 16:51           ` Peter Zijlstra
2019-05-31 18:58             ` Roman Penyaev
2019-06-03  9:09               ` Peter Zijlstra
2019-06-03 10:02                 ` Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 07/13] epoll: call ep_add_event_to_uring() from ep_poll_callback() Roman Penyaev
2019-05-31  9:56   ` Peter Zijlstra
2019-05-31 11:22     ` Roman Penyaev
2019-05-31 13:05       ` Peter Zijlstra
2019-05-31 15:05         ` Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 08/13] epoll: support polling from userspace for ep_insert() Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 09/13] epoll: support polling from userspace for ep_remove() Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 10/13] epoll: support polling from userspace for ep_modify() Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 11/13] epoll: support polling from userspace for ep_poll() Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 12/13] epoll: support mapping for epfd when polled from userspace Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 13/13] epoll: implement epoll_create2() syscall Roman Penyaev
2019-05-16 10:03   ` Arnd Bergmann
2019-05-16 10:20     ` Roman Penyaev
2019-05-16 10:57       ` Arnd Bergmann
2019-05-22  2:33       ` Andrew Morton
2019-05-22  9:11         ` Roman Penyaev
2019-05-22 11:14         ` Arnd Bergmann
2019-05-22 18:36           ` Andrew Morton
2019-05-31  9:55 ` [PATCH v3 00/13] epoll: support pollable epoll from userspace Peter Zijlstra
2019-05-31 14:48 ` Jens Axboe
2019-05-31 16:02   ` Roman Penyaev
2019-05-31 16:54     ` Jens Axboe
2019-05-31 19:45       ` Roman Penyaev
2019-05-31 21:09         ` Jens Axboe
2019-06-05  6:17           ` Roman Penyaev
2019-05-31 16:33 ` Peter Zijlstra
2019-05-31 18:50   ` Roman Penyaev

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