Re: [PATCH v2 06/14] elf: Use relaxed atomics for racy accesses [BZ #19329]

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

The 05/11/2021 10:31, Szabolcs Nagy via Libc-alpha wrote:
> Thanks for the review, i attached the fixed patch i plan to commit
> later today if there are no further comments.

committed as f4f8f4d4e0f92488431b268c8cd9555730b9afe9

and committed the other reviewed patches from the series too.

> From 2a65e592a753310334c1ded2841215fb9c6024f8 Mon Sep 17 00:00:00 2001
> From: Szabolcs Nagy <szabolcs.nagy@arm.com>
> Date: Wed, 30 Dec 2020 19:19:37 +0000
> Subject: [PATCH] elf: Use relaxed atomics for racy accesses [BZ #19329]
> 
> This is a follow up patch to the fix for bug 19329.  This adds relaxed
> MO atomics to accesses that were previously data races but are now
> race conditions, and where relaxed MO is sufficient.
> 
> The race conditions all follow the pattern that the write is behind the
> dlopen lock, but a read can happen concurrently (e.g. during tls access)
> without holding the lock.  For slotinfo entries the read value only
> matters if it reads from a synchronized write in dlopen or dlclose,
> otherwise the related dtv entry is not valid to access so it is fine
> to leave it in an inconsistent state.  The same applies for
> GL(dl_tls_max_dtv_idx) and GL(dl_tls_generation), but there the
> algorithm relies on the fact that the read of the last synchronized
> write is an increasing value.
> 
> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
...