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[PATCH] nptl: Document the reason why __kind in pthread_mutex_t is part of the ABI
- From: Florian Weimer <fweimer at redhat dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Mon, 7 Nov 2016 14:47:22 +0100
- Subject: [PATCH] nptl: Document the reason why __kind in pthread_mutex_t is part of the ABI
- Authentication-results: sourceware.org; auth=none
I started composing a lengthy email about why we should align
pthread_mutex_t layout on i386 and x86_64 (because cross-process
compatibility is of more practical importance these days than
LinuxThreads backwards compatibility). But then I realized that we
don't have this choice due to the static initializers, which have __kind
at different offsets.
The attached patch makes this more explicit in the relevant header files.
Thanks,
Florian
nptl: Document the reason why __kind in pthread_mutex_t is part of the ABI
2016-11-07 Florian Weimer <fweimer@redhat.com>
* sysdeps/aarch64/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Document ABI exposure of the __kind offset.
* sysdeps/arm/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Mention reason for the __kind offset exposure in the ABI.
* sysdeps/hppa/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
* sysdeps/ia64/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
* sysdeps/m68k/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
* sysdeps/microblaze/nptl/bits/pthreadtypes.h
(struct __pthread_mutex_s): Likewise.
* sysdeps/mips/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
* sysdeps/nios2/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
* sysdeps/s390/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
* sysdeps/sh/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
* sysdeps/sparc/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
* sysdeps/tile/nptl/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
* sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h
(struct __pthread_mutex_s): Likewise.
* sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h
(struct __pthread_mutex_s): Likewise.
* sysdeps/x86/bits/pthreadtypes.h (struct __pthread_mutex_s):
Likewise.
diff --git a/sysdeps/aarch64/nptl/bits/pthreadtypes.h b/sysdeps/aarch64/nptl/bits/pthreadtypes.h
index 13984a7..c376e64 100644
--- a/sysdeps/aarch64/nptl/bits/pthreadtypes.h
+++ b/sysdeps/aarch64/nptl/bits/pthreadtypes.h
@@ -65,6 +65,8 @@ typedef union
unsigned int __count;
int __owner;
unsigned int __nusers;
+ /* KIND must stay at this position in the structure to maintain
+ binary compatibility with static initializers. */
int __kind;
int __spins;
__pthread_list_t __list;
diff --git a/sysdeps/arm/nptl/bits/pthreadtypes.h b/sysdeps/arm/nptl/bits/pthreadtypes.h
index afb5392..645207b 100644
--- a/sysdeps/arm/nptl/bits/pthreadtypes.h
+++ b/sysdeps/arm/nptl/bits/pthreadtypes.h
@@ -64,7 +64,7 @@ typedef union
unsigned int __count;
int __owner;
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
unsigned int __nusers;
__extension__ union
diff --git a/sysdeps/hppa/nptl/bits/pthreadtypes.h b/sysdeps/hppa/nptl/bits/pthreadtypes.h
index 540802a..d0c1d58 100644
--- a/sysdeps/hppa/nptl/bits/pthreadtypes.h
+++ b/sysdeps/hppa/nptl/bits/pthreadtypes.h
@@ -71,7 +71,7 @@ typedef union
unsigned int __count;
int __owner;
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
/* The old 4-word 16-byte aligned lock. This is initalized
to all ones by the Linuxthreads PTHREAD_MUTEX_INITIALIZER.
diff --git a/sysdeps/ia64/nptl/bits/pthreadtypes.h b/sysdeps/ia64/nptl/bits/pthreadtypes.h
index f2e6dac..0e83883 100644
--- a/sysdeps/ia64/nptl/bits/pthreadtypes.h
+++ b/sysdeps/ia64/nptl/bits/pthreadtypes.h
@@ -64,7 +64,7 @@ typedef union
int __owner;
unsigned int __nusers;
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
int __spins;
__pthread_list_t __list;
diff --git a/sysdeps/m68k/nptl/bits/pthreadtypes.h b/sysdeps/m68k/nptl/bits/pthreadtypes.h
index d8faa7a..d195492 100644
--- a/sysdeps/m68k/nptl/bits/pthreadtypes.h
+++ b/sysdeps/m68k/nptl/bits/pthreadtypes.h
@@ -64,7 +64,7 @@ typedef union
unsigned int __count;
int __owner;
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
unsigned int __nusers;
__extension__ union
diff --git a/sysdeps/microblaze/nptl/bits/pthreadtypes.h b/sysdeps/microblaze/nptl/bits/pthreadtypes.h
index 9e9e307..2a1ca0a 100644
--- a/sysdeps/microblaze/nptl/bits/pthreadtypes.h
+++ b/sysdeps/microblaze/nptl/bits/pthreadtypes.h
@@ -63,7 +63,7 @@ typedef union
unsigned int __count;
int __owner;
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
unsigned int __nusers;
__extension__ union
diff --git a/sysdeps/mips/nptl/bits/pthreadtypes.h b/sysdeps/mips/nptl/bits/pthreadtypes.h
index 68ed94b..c7533a8 100644
--- a/sysdeps/mips/nptl/bits/pthreadtypes.h
+++ b/sysdeps/mips/nptl/bits/pthreadtypes.h
@@ -87,7 +87,7 @@ typedef union
unsigned int __nusers;
#endif
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
#if _MIPS_SIM == _ABI64
int __spins;
diff --git a/sysdeps/nios2/nptl/bits/pthreadtypes.h b/sysdeps/nios2/nptl/bits/pthreadtypes.h
index 76076d0..ee8b7ba 100644
--- a/sysdeps/nios2/nptl/bits/pthreadtypes.h
+++ b/sysdeps/nios2/nptl/bits/pthreadtypes.h
@@ -64,7 +64,7 @@ typedef union
unsigned int __count;
int __owner;
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
unsigned int __nusers;
__extension__ union
diff --git a/sysdeps/s390/nptl/bits/pthreadtypes.h b/sysdeps/s390/nptl/bits/pthreadtypes.h
index 40d10fe..21d13bd 100644
--- a/sysdeps/s390/nptl/bits/pthreadtypes.h
+++ b/sysdeps/s390/nptl/bits/pthreadtypes.h
@@ -86,7 +86,7 @@ typedef union
unsigned int __nusers;
#endif
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
#if __WORDSIZE == 64
# ifdef ENABLE_LOCK_ELISION
diff --git a/sysdeps/sh/nptl/bits/pthreadtypes.h b/sysdeps/sh/nptl/bits/pthreadtypes.h
index 13fbd73..5354f78 100644
--- a/sysdeps/sh/nptl/bits/pthreadtypes.h
+++ b/sysdeps/sh/nptl/bits/pthreadtypes.h
@@ -64,7 +64,7 @@ typedef union
unsigned int __count;
int __owner;
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
unsigned int __nusers;
__extension__ union
diff --git a/sysdeps/sparc/nptl/bits/pthreadtypes.h b/sysdeps/sparc/nptl/bits/pthreadtypes.h
index d45cb61..e781a25 100644
--- a/sysdeps/sparc/nptl/bits/pthreadtypes.h
+++ b/sysdeps/sparc/nptl/bits/pthreadtypes.h
@@ -87,7 +87,7 @@ typedef union
unsigned int __nusers;
#endif
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
#if __WORDSIZE == 64
int __spins;
diff --git a/sysdeps/tile/nptl/bits/pthreadtypes.h b/sysdeps/tile/nptl/bits/pthreadtypes.h
index 7d68650..b14b1c6 100644
--- a/sysdeps/tile/nptl/bits/pthreadtypes.h
+++ b/sysdeps/tile/nptl/bits/pthreadtypes.h
@@ -87,7 +87,7 @@ typedef union
unsigned int __nusers;
#endif
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
#if __WORDSIZE == 64
int __spins;
diff --git a/sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h b/sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h
index 1a1779b..b7af038 100644
--- a/sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h
+++ b/sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h
@@ -63,7 +63,7 @@ typedef union
int __owner;
unsigned int __nusers;
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
int __spins;
__pthread_list_t __list;
diff --git a/sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h b/sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h
index 345e79a..d230ac9 100644
--- a/sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h
+++ b/sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h
@@ -87,7 +87,7 @@ typedef union
unsigned int __nusers;
#endif
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
#if __WORDSIZE == 64
short __spins;
diff --git a/sysdeps/x86/bits/pthreadtypes.h b/sysdeps/x86/bits/pthreadtypes.h
index 16b8f4f..c641a40 100644
--- a/sysdeps/x86/bits/pthreadtypes.h
+++ b/sysdeps/x86/bits/pthreadtypes.h
@@ -98,7 +98,7 @@ typedef union
unsigned int __nusers;
#endif
/* KIND must stay at this position in the structure to maintain
- binary compatibility. */
+ binary compatibility with static initializers. */
int __kind;
#ifdef __x86_64__
short __spins;