Re: [PATCH 0/2] aarch64: non lazy tlsdesc

[Szabolcs Nagy <szabolcs dot nagy at arm dot com>]

On 06/10/17 15:22, Szabolcs Nagy wrote:
> lazy initialization of tlsdesc GOT entries is problematic on weak
> memory models, the data race was fixed by adding a synchronization
> barrier in the tlsdesc functions which run at every tls access:
> https://sourceware.org/ml/libc-alpha/2015-06/msg00496.html
> 
> this obviously has significant performance impact, so the real fix
> is to remove lazy initialization, which is not a useful feature,
> and drop all the complicated runtime code for it.
> 
> such a change would be useful to do generically for all tlsdesc
> targets (even where no barriers are needed for lazy initialization),
> but i did not see a clean way to special case tlsdesc relocs in
> the generic elf/do-rel.h code, so this is for aarch64 only (and
> i plan to submit a separate patch for arm too).
> 
> Szabolcs Nagy (2):
>   aarch64: Disable lazy symbol binding of TLSDESC
>   aarch64: Remove barriers from TLS descriptor functions
> 
>  elf/tlsdeschtab.h            |   2 +

i'd like to get review on this generic change in the second patch.

and waiting for comments whether a generic solution is desirable
or applying similar patch to arm is ok.

>  sysdeps/aarch64/dl-machine.h |  23 +++--
>  sysdeps/aarch64/dl-tlsdesc.S | 203 -------------------------------------------
>  sysdeps/aarch64/dl-tlsdesc.h |   9 --
>  sysdeps/aarch64/tlsdesc.c    | 127 +--------------------------
>  5 files changed, 17 insertions(+), 347 deletions(-)
>