Re: [PATCH v5 7/14] x86 support for Uprobes

[Oleg Nesterov <oleg@redhat.com>]

On 06/15, Srikar Dronamraju wrote:
>
> > I think it is OK to enable interrupts. do_notify_resume() calls do_signal()
> > which enables them anyway.
> >
> > But there is another question I already asked. Why the code uses
> > native_irq_enable()? IIRC, you explained that local_irq_enable() doesn't
> > work for unkown reason. This is strange, and imho should be explained.
>
> local_irq_enable() translates to raw_local_irq_enable().
> However raw_local_irq_enable on x86 seems to depend on CONFIG_PARAVIRT.
> On a machine, where CONFIG_PARAVIRT was defined, local_irq_enable
> translates to something other than native_irq_enable.
> It translates to PVOP_VCALLEE0(pv_irq_ops.irq_enable);

I see, and my question is why PVOP_VCALLEE0(pv_irq_ops.irq_enable) doesn't
work ? If it doesn't here, why it works for other callers of local_irq_enable?

I think we should ask paravirt developers.

> Is it okay to use local_irq_enable() and then make CONFIG_UPROBES depend
> on !CONFIG_PARAVIRT?

I dunno, and I know nothing about paravirt.

But please note that currently native_irq_enable has the only caller,
raw_local_irq_enable(). It is really strange that do_notify_resume()
has to use it, and it uses it to bypass the paravirt layer which perhaps
can introduce other problems.

Oleg.