Re: Hang on large copy_from_user with PREEMPT_NONE

[Ingo Molnar]

* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Mon, Apr 6, 2015 at 12:08 PM, Sasha Levin <sasha.levin@xxxxxxxxxx> wrote:
> >
> > Your patch just makes it hang in memset instead:
> 
> So it's certainly a big memset (2GB or so: original count in RDX: 
> 0x7e777000, and "%rcx << 6" is bytes left, so it has done about 85% 
> of it), which is certainly going to be slow, but it shouldn't 
> *hang*. [...]

Would be nice to see the actual kernel .config, as there's a few debug 
features that can slow things down significantly, such as 
CONFIG_KMEMCHECK=y or in some cases CONFIG_DEBUG_PAGEALLOC=y.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/