HPPA linux compat wrappers

Commit Message

Petr Salinger June 22, 2009, 1:29 p.m. UTC

>> I still think there should be support for mixed ABI calls.
>> See also thread http://lists.debian.org/debian-hppa/2008/09/msg00018.html
>
> It sounds like a good feature, but my time is restricted so I
> implemented the simplest interface possible that I could prove worked.
> If you have ample free time I suggest you post a version of the patch
> with your enhancements. I'd be more than willing to test your patches.

I have to admin I will not write the code, I only propose the idea.

1) put "__lt_compat" field in a place where originally is LT initializer.


2) create hppa specific pthread.h with just altered initializers (more zeroes)

3) At the begin of each affected function

>>  if (v->__lt_compat)
>>  {
>>     lock_global_pt_lock();
>>     if (v->__lt_compat)
>>     {
>>                zero_the_same_fields_as_NPTL_but_lt_compat_field();
>>                barrier();
>>                v->__lt_compat = 0;
>>     };
>>     unlock_global_pt_lock();
>>  };

This just atomically converts linuxthreads initialized variable into NPTL 
initialized variable.

>> For the new NPTL layout the zeroing code will not be taken,
>> therefore almost no overhead.
>> There might be a congestion on global_pt_lock, but I do not believe,
>> there are many static initilized mutexes in any real program.
>> There will be no need for allocation any new structures.
>
> There are tons of statically initialized mutexs, gnome and gdk are
> full of them as an example.

Hopefully not many will try to lock global_pt_lock in the same time.
Also rebuild against NPTL enabled libc-dev lowers the number
of possible linuxthreads initialized variables.

Petr

Patch

--- sysdeps/unix/sysv/linux/hppa/nptl/bits/pthreadtypes.h
+++ sysdeps/unix/sysv/linux/hppa/nptl/bits/pthreadtypes.h.compat 
@@ -70,6 +70,7 @@  pthread_mutex_t
      /* KIND must stay at this position in the structure to maintain
         binary compatibility.  */
      int __kind;
+    int __lt_compat;
      unsigned int __nusers;
      __extension__ union
      {
@@ -95,10 +96,11 @@  pthread_cond_t
    struct
    {
      int __lock;
-    unsigned int __futex;
+    int __lt_compat;
      __extension__ unsigned long long int __total_seq;
      __extension__ unsigned long long int __wakeup_seq;
      __extension__ unsigned long long int __woken_seq;
+    unsigned int __futex;
      void *__mutex;
      unsigned int __nwaiters;
      unsigned int __broadcast_seq;
@@ -130,6 +132,9 @@  pthread_rwlock_t
    struct
    {
      int __lock;
+    int __lt_compat;
+    int __hppa_pad1;
+    int __hppa_pad2;
      unsigned int __nr_readers;
      unsigned int __readers_wakeup;
      unsigned int __writer_wakeup;