Bug#842796: libc recently more aggressive about pthread locks in stable ?

[Lucas Nussbaum]

Hi,

On 06/11/16 at 17:41 -0200, Henrique de Moraes Holschuh wrote:
> On Sun, 06 Nov 2016, Ben Hutchings wrote:
> > It's worth noting that TSX is broken in 'Haswell' processors and is
> > supposed to be disabled via a microcode update.  I don't know whether
> > glibc avoids using it on these processors if the microcode update is
> > not applied.  (Linux doesn't appear to hide the feature flags.)
> 
> It does avoid it.  For glibc libpthreads, Debian has blacklisted Intel
> TSX use [in libpthreads] on all of Haswell and much of Broadwell.
> 
> But anything else *will* attempt to use it, people query cpuid directly
> for these things.  You need a hypervisor that filters cpuid().

How can one know what glibc does on a given CPU? (preferably without
access to the hardware)

I could try to run an archive rebuild on hardware where glibc leverages
TSX to see what happens.

Lucas