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Re: Support for i386 builds of glibc?
From: "Maciej W. Rozycki" <firstname.lastname@example.org>
Date: Mon, 4 Mar 2013 22:03:59 +0000
> On Mon, 4 Mar 2013, David Miller wrote:
>> > They could be easily emulated with the aid of global spinlocks, but
>> > given the decline of the i386 it's probably not worth the effort.
>> This is a misnomer, you can't use global spinlocks as those are not
>> signal safe and will deadlock. Even the glibc testsuite will trigger
>> such deadlocks.
> 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.