[PATCH 1/3] nptl: Move pthread_sigmask implementation to libc

[Florian Weimer]

* Adhemerval Zanella:

> On 13/03/2020 06:51, Florian Weimer wrote:
>> * Adhemerval Zanella via Libc-alpha:
>> 
>>> diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
>>> index a4c31932cb..694efeb1e4 100644
>>> --- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
>>> +++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
>>> @@ -1447,6 +1447,7 @@ GLIBC_2.17 pthread_self F
>>>  GLIBC_2.17 pthread_setcancelstate F
>>>  GLIBC_2.17 pthread_setcanceltype F
>>>  GLIBC_2.17 pthread_setschedparam F
>>> +GLIBC_2.17 pthread_sigmask F
>>>  GLIBC_2.17 ptrace F
>>>  GLIBC_2.17 ptsname F
>>>  GLIBC_2.17 ptsname_r F
>>> diff --git a/sysdeps/unix/sysv/linux/aarch64/libpthread.abilist b/sysdeps/unix/sysv/linux/aarch64/libpthread.abilist
>>> index d65beba958..48b368acb1 100644
>>> --- a/sysdeps/unix/sysv/linux/aarch64/libpthread.abilist
>>> +++ b/sysdeps/unix/sysv/linux/aarch64/libpthread.abilist
>>> @@ -156,7 +156,6 @@ GLIBC_2.17 pthread_setconcurrency F
>>>  GLIBC_2.17 pthread_setname_np F
>>>  GLIBC_2.17 pthread_setschedprio F
>>>  GLIBC_2.17 pthread_setspecific F
>>> -GLIBC_2.17 pthread_sigmask F
>>>  GLIBC_2.17 pthread_sigqueue F
>>>  GLIBC_2.17 pthread_spin_destroy F
>>>  GLIBC_2.17 pthread_spin_init F
>> 
>> This change is not fully compatible: Newly-linked programs may incur
>> lazy binding failures on older glibc versions because pthread_sigmask
>> is not present in libc.so.6.
>
> But backward compatibility is not a fully support scenario. Do we
> really need to handle such cases for the libpthread removal
> project?

So far, our approach to symbol versioning has been that if the
application (or DSO) loads, it will not fail later due to a missing
symbol.  Some RPM-based distributions have no other mechanism to
ensure correct package dependencies.