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From: Zach Brown <>
To: Rusty Russell <>
	Linus Torvalds <>,
	Ingo Molnar <>, Ulrich Drepper <>,
	Arjan van de Ven <>,
	Andrew Morton <>,
	Alan Cox <>,
	Evgeniy Polyakov <>,
	"David S. Miller" <>,
	Suparna Bhattacharya <>,
	Davide Libenzi <>,
	Jens Axboe <>,
	Thomas Gleixner <>,
	Dan Williams <>,
	Jeff Moyer <>,
	Simon Holm Thogersen <>,
Subject: Re: [PATCH 5/6] syslets: add generic syslets infrastructure
Date: Tue, 08 Jan 2008 19:00:04 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

>     Firstly, why not just specify an address for the return value and be done 
> with it?  This infrastructure seems overkill, and you can always extend later 
> if required.

Sorry, which infrastructure?

Providing the function and stack to return to?  Sure, I could certainly
entertain the idea of not having syslet tasks return to userspace in the
first pass.  Ingo sure seemed excited by the idea.

Or do you mean the syscall return value ending up in the userspace
completion event ring?  That's mostly about being able to wait for
pending syslets to complete.

> Secondly, you really should allow integration with an eventfd so you don't 
> make the posix AIO mistake of providing a poll-incompatible interface.

Yeah, this seems straight forward enough that I haven't made it an
initial priority.  I'm sure it will be helpful for people who are stuck
integrating with entrenched software that wants to wait for pollable fds.

For more flexible software, though, it's compelling to now be able to
aggregate waiting for completion of the existing waiting syscalls (poll,
epoll_wait, futexes, whatever) by issuing them as concurrent syslets.

> Finally, and probably most alarmingly, AFAICT randomly changing TID will break 
> all threaded programs, which means this won't be fitted into existing code 
> bases, making it YA niche Linux-only API 8(

Yeah, this still needs to be investigated.  I haven't yet and I haven't
heard of anyone else trying their hand at it.

In the YANLOA mode apps would know that executing syslets is an implicit
clone() and would act accordingly.  "8(", indeed.

I wonder if there isn't an opportunity to add a clone() flag which
juggles the association between TIDs and task_structs.  I don't relish
the idea of investigating the life cycles of task_struct references that
derive from TIDs and seeing how those would race with a syslet blocking
and cloning, but, well, maybe that's what needs to be done.

This all isn't my area of expertise, though, sadly.  It would be swell
if someone wanted to look into it before I'm forced to learn yet another
weird corner of the kernel.

- z

  reply	other threads:[~2008-01-09  3:00 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-06 23:20 syslets v7: back to basics Zach Brown
2007-12-06 23:20 ` [PATCH 1/6] indirect: use asmlinkage in i386 syscall table prototype Zach Brown
2007-12-06 23:20   ` [PATCH 2/6] syslet: asm-generic support to disable syslets Zach Brown
2007-12-06 23:20     ` [PATCH 3/6] syslet: introduce abi structs Zach Brown
2007-12-06 23:20       ` [PATCH 4/6] syslets: add indirect args Zach Brown
2007-12-06 23:20         ` [PATCH 5/6] syslets: add generic syslets infrastructure Zach Brown
2007-12-06 23:20           ` [PATCH 6/6] syslets: add both 32bit and 64bit x86 syslet support Zach Brown
2007-12-07 11:55           ` [PATCH 5/6] syslets: add generic syslets infrastructure Evgeniy Polyakov
2007-12-07 18:24             ` Zach Brown
2008-01-09  2:03           ` Rusty Russell
2008-01-09  3:00             ` Zach Brown [this message]
2008-01-09  3:48               ` Rusty Russell
2008-01-09 18:16                 ` Zach Brown
2008-01-09 22:04                   ` Rusty Russell
2008-01-09 22:58                     ` Linus Torvalds
2008-01-09 23:05                       ` Linus Torvalds
2008-01-09 23:47                       ` Zach Brown
2008-01-10  1:18                       ` Rusty Russell
2008-01-09 23:15                     ` Davide Libenzi
2008-01-10  5:41                   ` Jeff Garzik
2007-12-08 12:40   ` [PATCH 1/6] indirect: use asmlinkage in i386 syscall table prototype Simon Holm Thøgersen
2007-12-08 21:22     ` Zach Brown
2007-12-08 12:52 ` [PATCH] Fix casting on architectures with 32-bit pointers/longs Simon Holm Thøgersen
2007-12-10 19:46 ` syslets v7: back to basics Jens Axboe
2007-12-10 21:30 ` Phillip Susi
2007-12-10 22:15   ` Zach Brown

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