linux-kernel - Re: [PATCH v2 04/10] um: Turn signals

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Message-Id: <20250911043434.2897892-1-tiwei.bie@linux.dev>
Date: Thu, 11 Sep 2025 12:34:34 +0800
From: Tiwei Bie <tiwei.bie@...ux.dev>
To: johannes@...solutions.net
Cc: richard@....at,
	anton.ivanov@...bridgegreys.com,
	benjamin@...solutions.net,
	arnd@...db.de,
	linux-um@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	tiwei.btw@...group.com,
	tiwei.bie@...ux.dev
Subject: Re: [PATCH v2 04/10] um: Turn signals_* into thread-local variables

On Wed, 10 Sep 2025 14:15:28 +0200, Johannes Berg wrote:
> On Sun, 2025-08-10 at 13:51 +0800, Tiwei Bie wrote:
> > From: Tiwei Bie <tiwei.btw@...group.com>
> > 
> > Turn signals_enabled, signals_pending and signals_active into
> > thread-local variables. This enables us to control and track
> > signals independently on each CPU thread. This is a preparation
> > for adding SMP support.
> 
> [...]
> 
> > +static __thread int signals_enabled;
> 
> How much glibc infrastructure does __thread rely on? More specifically:
> Some time ago we had a discussion about building UML as a nolibc binary,
> what would that mean for the __thread usage here?

We would need to parse TLS data (PT_TLS) from the ELF file ourselves
and properly set up TLS when creating threads using clone().

Regards,
Tiwei