Re: Support for i386 builds of glibc?

[David Miller <davem at davemloft dot net>]

From: "Maciej W. Rozycki" <macro@codesourcery.com>
Date: Mon, 4 Mar 2013 23:03:11 +0000

> On Mon, 4 Mar 2013, David Miller wrote:
> 
>> >  I think "can't" is too strong a statement, signals are to userland what 
>> > interrupts are to the kernel.  The whole critical section could run with 
>> > all signals blocked; if you wrote that the overhead might be prohibitive, 
>> > then I would agree though.
>> 
>> You can't mess with signal state in the lock handlers, think about
>> siglongjmp and friends.
>> 
>> It's impossible even if you're willing to accept prohibitive cost.
> 
>  I don't believe it.  Can you provide me with an example where a sequence 
> like:

Yep, that would seemingly work.

Next, what if the manual cmpxchg faults and the signal handler
wants to take this lock to report the SIGSEGV to the user?