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Re: Correct robust mutex / PI futex kernel assumptions (bug 9894)

From: "Joseph S. Myers" <joseph at codesourcery dot com>
To: David Miller <davem at davemloft dot net>
Cc: <libc-alpha at sourceware dot org>, <schwab at linux-m68k dot org>, <david dot holsgrove at xilinx dot com>, <aurel32 at debian dot org>
Date: Tue, 25 Mar 2014 23:20:00 +0000
Subject: Re: Correct robust mutex / PI futex kernel assumptions (bug 9894)
Authentication-results: sourceware.org; auth=none
References: <Pine dot LNX dot 4 dot 64 dot 1403251526170 dot 15671 at digraph dot polyomino dot org dot uk> <20140325 dot 180932 dot 680988348665832310 dot davem at davemloft dot net> <Pine dot LNX dot 4 dot 64 dot 1403252247450 dot 10779 at digraph dot polyomino dot org dot uk> <20140325 dot 190632 dot 1279135735148309574 dot davem at davemloft dot net>

On Tue, 25 Mar 2014, David Miller wrote:

> Actually, it turns out you can simply test for the CPP macro __sparc_v9__

In that case, here is a revised patch using __sparc_v9__ in place of 
__arch64__.

2014-03-25  Joseph Myers  <joseph@codesourcery.com>

	[BZ #9894]
	* sysdeps/unix/sysv/linux/kernel-features.h
	[__sparc__ && !__sparc_v9__] (__ASSUME_SET_ROBUST_LIST): Do not
	define.
	[__sparc__ && !__sparc_v9__] (__ASSUME_FUTEX_LOCK_PI): Likewise.
	[__sparc__ && !__sparc_v9__] (__ASSUME_REQUEUE_PI): Likewise.
	* sysdeps/unix/sysv/linux/arm/kernel-features.h
	(__ASSUME_FUTEX_LOCK_PI): Undefine.
	(__ASSUME_REQUEUE_PI): Likewise.
	(__ASSUME_SET_ROBUST_LIST): Likewise.
	* sysdeps/unix/sysv/linux/m68k/kernel-features.h
	[__LINUX_KERNEL_VERSION < 0x030a00] (__ASSUME_FUTEX_LOCK_PI):
	Undefine.
	* sysdeps/unix/sysv/linux/microblaze/kernel-features.h
	[__LINUX_KERNEL_VERSION < 0x020621] (__ASSUME_FUTEX_LOCK_PI):
	Likewise.
	[__LINUX_KERNEL_VERSION < 0x020621] (__ASSUME_REQUEUE_PI):
	Likewise.
	[__LINUX_KERNEL_VERSION < 0x020621] (__ASSUME_SET_ROBUST_LIST):
	Likewise.
	* sysdeps/unix/sysv/linux/mips/kernel-features.h
	[__mips == 1 || _MIPS_ARCH_R5900] (__ASSUME_FUTEX_LOCK_PI):
	Undefine.
	[__mips == 1 || _MIPS_ARCH_R5900] (__ASSUME_REQUEUE_PI): Likewise.
	[__mips == 1 || _MIPS_ARCH_R5900] (__ASSUME_SET_ROBUST_LIST):
	Likewise.

diff --git a/sysdeps/unix/sysv/linux/arm/kernel-features.h b/sysdeps/unix/sysv/linux/arm/kernel-features.h
index 401343b..96b7350 100644
--- a/sysdeps/unix/sysv/linux/arm/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/arm/kernel-features.h
@@ -53,3 +53,10 @@
 # undef __ASSUME_PSELECT
 # undef __ASSUME_PPOLL
 #endif
+
+/* The ARM kernel may or may not support
+   futex_atomic_cmpxchg_inatomic, depending on kernel
+   configuration.  */
+#undef __ASSUME_FUTEX_LOCK_PI
+#undef __ASSUME_REQUEUE_PI
+#undef __ASSUME_SET_ROBUST_LIST
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 555b82c..a1853c3 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -106,9 +106,12 @@
 # define __ASSUME_ATFCTS	1
 #endif
 
-/* Support for inter-process robust mutexes was added in 2.6.17.  */
+/* Support for inter-process robust mutexes was added in 2.6.17 (but
+   some architectures lack futex_atomic_cmpxchg_inatomic in some
+   configurations).  */
 #if __LINUX_KERNEL_VERSION >= 0x020611 \
-    && (!defined __sh__ || __LINUX_KERNEL_VERSION >= 0x020613)
+    && (!defined __sh__ || __LINUX_KERNEL_VERSION >= 0x020613) \
+    && !(defined __sparc__ && !defined __sparc_v9__)
 # define __ASSUME_SET_ROBUST_LIST	1
 #endif
 
@@ -119,8 +122,10 @@
 # define __ASSUME_COMPLETE_READV_WRITEV	1
 #endif
 
-/* Support for PI futexes was added in 2.6.18.  */
-#if __LINUX_KERNEL_VERSION >= 0x020612
+/* Support for PI futexes was added in 2.6.18 (but some architectures
+   lack futex_atomic_cmpxchg_inatomic in some configurations).  */
+#if __LINUX_KERNEL_VERSION >= 0x020612 \
+    && !(defined __sparc__ && !defined __sparc_v9__)
 # define __ASSUME_FUTEX_LOCK_PI	1
 #endif
 
@@ -223,8 +228,11 @@
 # define __ASSUME_PWRITEV	1
 #endif
 
-/* Support for FUTEX_*_REQUEUE_PI was added in 2.6.31.  */
-#if __LINUX_KERNEL_VERSION >= 0x02061f
+/* Support for FUTEX_*_REQUEUE_PI was added in 2.6.31 (but some
+   architectures lack futex_atomic_cmpxchg_inatomic in some
+   configurations).  */
+#if __LINUX_KERNEL_VERSION >= 0x02061f \
+    && !(defined __sparc__ && !defined __sparc_v9__)
 # define __ASSUME_REQUEUE_PI	1
 #endif
 
diff --git a/sysdeps/unix/sysv/linux/m68k/kernel-features.h b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
index cb8915f..bc340bd 100644
--- a/sysdeps/unix/sysv/linux/m68k/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
@@ -48,6 +48,7 @@
 
 /* No support for PI futexes or robust mutexes before 3.10 for m68k.  */
 #if __LINUX_KERNEL_VERSION < 0x030a00
+# undef __ASSUME_FUTEX_LOCK_PI
 # undef __ASSUME_REQUEUE_PI
 # undef __ASSUME_SET_ROBUST_LIST
 #endif
diff --git a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
index f9a61a9..a62b839 100644
--- a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
@@ -43,6 +43,13 @@
 
 #include_next <kernel-features.h>
 
+/* Support for futex_atomic_cmpxchg_inatomic was added in 2.6.33.  */
+#if __LINUX_KERNEL_VERSION < 0x020621
+# undef __ASSUME_FUTEX_LOCK_PI
+# undef __ASSUME_REQUEUE_PI
+# undef __ASSUME_SET_ROBUST_LIST
+#endif
+
 /* The MicroBlaze kernel does not support the pselect6, preadv and
    pwritev syscalls.  */
 #undef __ASSUME_PSELECT
diff --git a/sysdeps/unix/sysv/linux/mips/kernel-features.h b/sysdeps/unix/sysv/linux/mips/kernel-features.h
index 52cbf3a..19d3cba 100644
--- a/sysdeps/unix/sysv/linux/mips/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/mips/kernel-features.h
@@ -53,3 +53,11 @@
 #if _MIPS_SIM == _ABIN32 && __LINUX_KERNEL_VERSION < 0x020623
 # undef __ASSUME_GETDENTS64_SYSCALL
 #endif
+
+/* The MIPS kernel does not support futex_atomic_cmpxchg_inatomic if
+   emulating LL/SC.  */
+#if __mips == 1 || defined _MIPS_ARCH_R5900
+# undef __ASSUME_FUTEX_LOCK_PI
+# undef __ASSUME_REQUEUE_PI
+# undef __ASSUME_SET_ROBUST_LIST
+#endif

-- 
Joseph S. Myers
joseph@codesourcery.com

Follow-Ups:
- Re: Correct robust mutex / PI futex kernel assumptions (bug 9894)
  - From: David Miller

References:
- Re: Correct robust mutex / PI futex kernel assumptions (bug 9894)
  - From: Joseph S. Myers
- Re: Correct robust mutex / PI futex kernel assumptions (bug 9894)
  - From: David Miller
- Re: Correct robust mutex / PI futex kernel assumptions (bug 9894)
  - From: Joseph S. Myers
- Re: Correct robust mutex / PI futex kernel assumptions (bug 9894)
  - From: David Miller

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