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From: Richard Weinberger <richard@nod.at>
To: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: linux-um@lists.infradead.org
Subject: Re: [PATCH] um: Try to avoid kmalloc in signal handling
Date: Fri, 04 Jan 2019 11:33:57 +0100	[thread overview]
Message-ID: <9157944.H6u4diqB1j@blindfold> (raw)
In-Reply-To: <108ad3b6-93ee-5d8c-c1bf-b83e22ff3d3f@cambridgegreys.com>

Am Freitag, 4. Januar 2019, 11:19:46 CET schrieb Anton Ivanov:
> > I fear this is not correct.
> > Think of task switching, if you push something to reg_file[],
> > it is not guaranteed that the same task will run next and pop the item.
> > The order can change.
> 
> It should not occur for the signals that map onto IRQ (timer and IO) - 
> there it is all kernel.
> 
> I cannot trigger that for the other ones, but it may be possible.

We need to be super sure about this.
 
> IMO we should just bite the bullet and go back to using the stack 
> increasing the minimum stack order needed to 1 for 32 bit and to 2 for 
> 64 bit.

Increasing the kernel stack just for this is also a huge overhead.
But I never benchmarked it myself.

> x86 if I read it correctly is still using the stack even for the new 
> register sets.

Are you sure? I don't think so. The kernel stack is small and the xregset is
huge.
Where did you see this?

Thanks,
//richard



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  reply	other threads:[~2019-01-04 10:34 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-04 10:05 [PATCH] um: Try to avoid kmalloc in signal handling anton.ivanov
2019-01-04 10:13 ` Richard Weinberger
2019-01-04 10:19   ` Anton Ivanov
2019-01-04 10:33     ` Richard Weinberger [this message]
2019-01-04 10:49       ` Anton Ivanov
2019-01-04 11:31       ` Anton Ivanov
  -- strict thread matches above, loose matches on Subject: below --
2019-01-03 16:09 anton.ivanov
2019-01-03 17:13 ` Anton Ivanov
2019-01-03 21:29   ` Anton Ivanov
2019-01-03 21:42     ` Richard Weinberger
2019-01-04  7:07       ` Anton Ivanov
2019-01-04  7:48       ` Anton Ivanov
2019-01-04 15:50       ` Anton Ivanov
2019-01-07 10:07         ` Anton Ivanov

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