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[PATCH 05/11] Disable elision for PTHREAD_MUTEX_NORMAL mutexes
- From: Andi Kleen <andi at firstfloor dot org>
- To: libc-alpha at sourceware dot org
- Cc: Andi Kleen <ak at linux dot jf dot intel dot com>
- Date: Mon, 24 Jun 2013 11:24:44 -0700
- Subject: [PATCH 05/11] Disable elision for PTHREAD_MUTEX_NORMAL mutexes
- References: <1372098290-29147-1-git-send-email-andi at firstfloor dot org>
From: Andi Kleen <ak@linux.intel.com>
There was a lot of discussion about the POSIX statement that
PTHREAD_MUTEX_NORMAL "shall" deadlock for mutexes that
get re-acquired by the same thread.
Elided mutexes act like recursive locks and would only deadlock
sometimes (any time an abort happens, e.g. at program startup
or when context switches or syscalls happen), but not guaranteed
every time.
This does not apply to DEFAULT mutexes. But currently in glibc DEFAULT and
NORMAL is the same number.
The only way NORMAL can be set is through pthread_mutexattr_setkind()
PTHREAD_MUTEX_INITIALIZER initialized mutexes are default.
So what we do here is:
- Add a new numeric value for PTHREAD_MUTEX_NORMAL
- Add a new symbol version for pthread_mutexattr_setkind
(and its aliases pthread_mutexattr_settype_np and __pthread_mutexattr_settype)
that disables elision for the new PTHREAD_MUTEX_NORMAL value
- The compat version for the old symbol version always
disables elision when a 0 type (old ambigious DEFUALT/NORMAL)
is passed.
The result is that old binaries that use pthread_mutexattr_setkind()
for NORMAL/DEFAULT/TIMED_NP will disable elision, and new programs that
use it with PTHREAD_MUTEX_NORMAL only (but not default/timed) will
also disable elision. Any mutex not using pthread_mutexattr_setkind
or setting an ADAPTIVE type uses elision. The use of
pthread_mutexattr_setkind() for the default type is expected to be
rare, so this should not affect many programs.
Note an alternative would be to just disable nesting for these
normal mutexes (so always _xabort() before starting a transaction).
This would require additional checks in the fast path, and
since this case should be rare we just disable elision instead.
This adds new symbol versions to pthread, so the ABI test
files needed to be updated.
Thanks to Torvald Riegel, Roland McGrath, Richard Henderson, Rich Felker
for input on the discussion. This patch is based on the proposal from
Rich Felker, with some help from H.J. on the aliases.
nptl/:
2013-06-21 Andi Kleen <ak@linux.intel.com>
H.J. Lu <hongjiu.lu@intel.com>
Rich Felker <dalias@aerifal.cx>
* Versions (pthread_mutexattr_settype,
pthread_mutexattr_setkind_np, __pthread_mutexattr_settype): Add
new version for GLIBC_2.18.
* pthreadP.h: Use PTHREAD_MUTEX_DEFAULT to define derived
NORMAL mutexes. These disable elision in any case.
* pthread_mutexattr_init.c (pthread_mutexattr_init):
Use PTHREAD_MUTEX_DEFAULT instead of PTHREAD_MUTEX_NORMAL.
* pthread_mutex_init.c (default_mutexattr): Use
PTHREAD_MUTEX_DEFAULT as base value.
(__pthread_mutex_init): Disable elision flags for
prio/robust.
* pthread_mutexattr_settype.c
(pthread_mutexattr_settype_worker): Rename from
__pthread_mutexattr_settype.
(__pthread_mutexattr_settype_new):
Add new symbol version. Disable lock elision for NORMAL type.
(__pthread_mutexattr_settype_old): New function to disable lock
elision for old DEFAULT/NORMAL/TIMED type.
* sysdeps/pthread/pthread.h (PTHREAD_MUTEX_NORMAL): Redefine
as new value.
* tst-mutex5.c: Use PTHREAD_MUTEX_DEFAULT.
* sysdeps/unix/sysv/linux/x86_64/64/nptl/libpthread.abilist:
Update.
---
nptl/Versions | 6 +-
nptl/pthreadP.h | 4 +-
nptl/pthread_mutex_init.c | 11 +++-
nptl/pthread_mutexattr_init.c | 2 +-
nptl/pthread_mutexattr_settype.c | 74 +++++++++++++++++++---
nptl/sysdeps/pthread/pthread.h | 11 +++-
nptl/tst-mutex5.c | 2 +-
.../unix/sysv/linux/i386/nptl/libpthread.abilist | 3 +
.../powerpc/powerpc32/fpu/nptl/libpthread.abilist | 3 +
.../powerpc/powerpc64/nptl/libpthread.abilist | 3 +
.../linux/s390/s390-32/nptl/libpthread.abilist | 3 +
.../linux/s390/s390-64/nptl/libpthread.abilist | 3 +
sysdeps/unix/sysv/linux/sh/nptl/libpthread.abilist | 3 +
.../linux/sparc/sparc32/nptl/libpthread.abilist | 3 +
.../linux/sparc/sparc64/nptl/libpthread.abilist | 3 +
.../sysv/linux/x86_64/64/nptl/libpthread.abilist | 3 +
.../sysv/linux/x86_64/x32/nptl/libpthread.abilist | 4 ++
17 files changed, 124 insertions(+), 17 deletions(-)
diff --git a/nptl/Versions b/nptl/Versions
index bb11277..7a3da25 100644
--- a/nptl/Versions
+++ b/nptl/Versions
@@ -255,7 +255,11 @@ libpthread {
GLIBC_2.18 {
pthread_getattr_default_np;
pthread_setattr_default_np;
- }
+ /* Changed value of PTHREAD_MUTEX_NORMAL. */
+ pthread_mutexattr_settype;
+ pthread_mutexattr_setkind_np;
+ __pthread_mutexattr_settype;
+ };
GLIBC_PRIVATE {
__pthread_initialize_minimal;
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index 10b4be8..cbf26ca 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -70,7 +70,7 @@ enum
= PTHREAD_MUTEX_ROBUST_NORMAL_NP | PTHREAD_MUTEX_ADAPTIVE_NP,
PTHREAD_MUTEX_PRIO_INHERIT_NP = 32,
PTHREAD_MUTEX_PI_NORMAL_NP
- = PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_NORMAL,
+ = PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_DEFAULT,
PTHREAD_MUTEX_PI_RECURSIVE_NP
= PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_RECURSIVE_NP,
PTHREAD_MUTEX_PI_ERRORCHECK_NP
@@ -87,7 +87,7 @@ enum
= PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP,
PTHREAD_MUTEX_PRIO_PROTECT_NP = 64,
PTHREAD_MUTEX_PP_NORMAL_NP
- = PTHREAD_MUTEX_PRIO_PROTECT_NP | PTHREAD_MUTEX_NORMAL,
+ = PTHREAD_MUTEX_PRIO_PROTECT_NP | PTHREAD_MUTEX_DEFAULT,
PTHREAD_MUTEX_PP_RECURSIVE_NP
= PTHREAD_MUTEX_PRIO_PROTECT_NP | PTHREAD_MUTEX_RECURSIVE_NP,
PTHREAD_MUTEX_PP_ERRORCHECK_NP
diff --git a/nptl/pthread_mutex_init.c b/nptl/pthread_mutex_init.c
index 174d900..f6f0f80 100644
--- a/nptl/pthread_mutex_init.c
+++ b/nptl/pthread_mutex_init.c
@@ -26,8 +26,8 @@
static const struct pthread_mutexattr default_mutexattr =
{
- /* Default is a normal mutex, not shared between processes. */
- .mutexkind = PTHREAD_MUTEX_NORMAL
+ /* Default is a default mutex, not shared between processes. */
+ .mutexkind = PTHREAD_MUTEX_DEFAULT
};
@@ -129,6 +129,13 @@ __pthread_mutex_init (mutex, mutexattr)
| PTHREAD_MUTEXATTR_FLAG_ROBUST)) != 0)
mutex->__data.__kind |= PTHREAD_MUTEX_PSHARED_BIT;
+ /* Drop elision bits for any unusual flags, except for PSHARED.
+ These can be set implicitely now, but the other code paths don't
+ expect them for all cases. */
+ if ((mutex->__data.__kind &
+ (PTHREAD_MUTEXATTR_FLAG_BITS & ~PTHREAD_MUTEXATTR_FLAG_PSHARED)))
+ mutex->__data.__kind &= ~PTHREAD_MUTEX_ELISION_FLAGS_NP;
+
/* Default values: mutex not used yet. */
// mutex->__count = 0; already done by memset
// mutex->__owner = 0; already done by memset
diff --git a/nptl/pthread_mutexattr_init.c b/nptl/pthread_mutexattr_init.c
index b08eeab..0c955f1 100644
--- a/nptl/pthread_mutexattr_init.c
+++ b/nptl/pthread_mutexattr_init.c
@@ -30,7 +30,7 @@ __pthread_mutexattr_init (attr)
/* We use bit 31 to signal whether the mutex is going to be
process-shared or not. By default it is zero, i.e., the mutex is
not process-shared. */
- ((struct pthread_mutexattr *) attr)->mutexkind = PTHREAD_MUTEX_NORMAL;
+ ((struct pthread_mutexattr *) attr)->mutexkind = PTHREAD_MUTEX_DEFAULT;
return 0;
}
diff --git a/nptl/pthread_mutexattr_settype.c b/nptl/pthread_mutexattr_settype.c
index 92772e6..8897653 100644
--- a/nptl/pthread_mutexattr_settype.c
+++ b/nptl/pthread_mutexattr_settype.c
@@ -18,27 +18,85 @@
#include <errno.h>
#include <pthreadP.h>
+#include <shlib-compat.h>
-
-int
-__pthread_mutexattr_settype (attr, kind)
- pthread_mutexattr_t *attr;
- int kind;
+static int
+pthread_mutexattr_settype_worker (pthread_mutexattr_t *attr, int kind)
{
struct pthread_mutexattr *iattr;
int mkind = kind & ~PTHREAD_MUTEX_ELISION_FLAGS_NP;
- if (mkind < PTHREAD_MUTEX_NORMAL || mkind > PTHREAD_MUTEX_ADAPTIVE_NP)
+ if (mkind < PTHREAD_MUTEX_TIMED_NP || mkind > PTHREAD_MUTEX_NORMAL)
return EINVAL;
/* Cannot set multiple flags. */
if ((kind & PTHREAD_MUTEX_ELISION_FLAGS_NP) == PTHREAD_MUTEX_ELISION_FLAGS_NP)
return EINVAL;
+ /* When a NORMAL mutex is explicitly specified, default to no elision
+ to satisfy POSIX's deadlock requirement. Also convert the NORMAL
+ type to DEFAULT, as the rest of the lock library doesn't have
+ the code paths for them. */
+ if (mkind == PTHREAD_MUTEX_NORMAL)
+ {
+ kind = PTHREAD_MUTEX_DEFAULT | (kind & PTHREAD_MUTEX_ELISION_FLAGS_NP);
+ if ((kind & PTHREAD_MUTEX_ELISION_FLAGS_NP) == 0)
+ kind |= PTHREAD_MUTEX_NO_ELISION_NP;
+ }
+
iattr = (struct pthread_mutexattr *) attr;
iattr->mutexkind = (iattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_BITS) | kind;
return 0;
}
-weak_alias (__pthread_mutexattr_settype, pthread_mutexattr_setkind_np)
-strong_alias (__pthread_mutexattr_settype, pthread_mutexattr_settype)
+
+int
+__pthread_mutexattr_settype_new (pthread_mutexattr_t *attr, int kind)
+{
+ return pthread_mutexattr_settype_worker (attr, kind);
+}
+
+weak_alias (__pthread_mutexattr_settype_new, __new_pthread_mutexattr_setkind_np)
+strong_alias (__pthread_mutexattr_settype_new, __new_pthread_mutexattr_settype)
+
+versioned_symbol (libpthread, __new_pthread_mutexattr_setkind_np,
+ pthread_mutexattr_setkind_np, GLIBC_2_18);
+versioned_symbol (libpthread, __new_pthread_mutexattr_settype,
+ pthread_mutexattr_settype, GLIBC_2_18);
+versioned_symbol (libpthread, __pthread_mutexattr_settype_new,
+ __pthread_mutexattr_settype, GLIBC_2_18);
+
+#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_18) \
+ || SHLIB_COMPAT (libpthread, GLIBC_2_1, GLIBC_2_18) \
+
+int
+attribute_compat_text_section
+__pthread_mutexattr_settype_old (pthread_mutexattr_t *attr, int kind)
+{
+ /* Force no elision for the old ambigious DEFAULT/NORMAL
+ kind. */
+ if (kind == PTHREAD_MUTEX_DEFAULT)
+ kind |= PTHREAD_MUTEX_NO_ELISION_NP;
+ return pthread_mutexattr_settype_worker (attr, kind);
+}
+
+
+# if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_18)
+weak_alias (__pthread_mutexattr_settype_old, __old_pthread_mutexattr_setkind_np)
+strong_alias (__pthread_mutexattr_settype_old, __old_pthread_mutexattr_settype)
+compat_symbol (libpthread,
+ __old_pthread_mutexattr_setkind_np,
+ pthread_mutexattr_setkind_np,
+ GLIBC_2_0);
+compat_symbol (libpthread,
+ __old_pthread_mutexattr_settype,
+ __pthread_mutexattr_settype,
+ GLIBC_2_0);
+# endif
+# if SHLIB_COMPAT (libpthread, GLIBC_2_1, GLIBC_2_18)
+compat_symbol (libpthread,
+ __pthread_mutexattr_settype_old,
+ pthread_mutexattr_settype,
+ GLIBC_2_1);
+# endif
+#endif
diff --git a/nptl/sysdeps/pthread/pthread.h b/nptl/sysdeps/pthread/pthread.h
index 485a865..adc259e 100644
--- a/nptl/sysdeps/pthread/pthread.h
+++ b/nptl/sysdeps/pthread/pthread.h
@@ -46,6 +46,14 @@ enum
PTHREAD_MUTEX_ERRORCHECK_NP,
PTHREAD_MUTEX_ADAPTIVE_NP,
+#if defined __USE_UNIX98 || defined __USE_XOPEN2K8
+ /* Before glibc 2.18 this used to be identical to TIMED_NP.
+ Now with lock elision it's a new type that does not enable
+ elision when set by pthread_mutexattr_settype(), to satisfy
+ POSIX's deadlock requirement. */
+ PTHREAD_MUTEX_NORMAL,
+#endif
+
PTHREAD_MUTEX_ELISION_NP = 1024,
PTHREAD_MUTEX_NO_ELISION_NP = 2048,
PTHREAD_MUTEX_UPGRADED_ELISION_NP = 4096,
@@ -53,10 +61,9 @@ enum
#if defined __USE_UNIX98 || defined __USE_XOPEN2K8
,
- PTHREAD_MUTEX_NORMAL = PTHREAD_MUTEX_TIMED_NP,
PTHREAD_MUTEX_RECURSIVE = PTHREAD_MUTEX_RECURSIVE_NP,
PTHREAD_MUTEX_ERRORCHECK = PTHREAD_MUTEX_ERRORCHECK_NP,
- PTHREAD_MUTEX_DEFAULT = PTHREAD_MUTEX_NORMAL
+ PTHREAD_MUTEX_DEFAULT = PTHREAD_MUTEX_TIMED_NP
#endif
#ifdef __USE_GNU
/* For compatibility. */
diff --git a/nptl/tst-mutex5.c b/nptl/tst-mutex5.c
index f19cd8c..df6564b 100644
--- a/nptl/tst-mutex5.c
+++ b/nptl/tst-mutex5.c
@@ -25,7 +25,7 @@
#ifndef TYPE
-# define TYPE PTHREAD_MUTEX_NORMAL
+# define TYPE PTHREAD_MUTEX_DEFAULT
#endif
diff --git a/sysdeps/unix/sysv/linux/i386/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/i386/nptl/libpthread.abilist
index 865364e..3437fde 100644
--- a/sysdeps/unix/sysv/linux/i386/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/i386/nptl/libpthread.abilist
@@ -176,7 +176,10 @@ GLIBC_2.12
pthread_setname_np F
GLIBC_2.18
GLIBC_2.18 A
+ __pthread_mutexattr_settype F
pthread_getattr_default_np F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
pthread_setattr_default_np F
GLIBC_2.2
GLIBC_2.2 A
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/nptl/libpthread.abilist
index c8a2a04..6927ce1 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/nptl/libpthread.abilist
@@ -176,7 +176,10 @@ GLIBC_2.12
pthread_setname_np F
GLIBC_2.18
GLIBC_2.18 A
+ __pthread_mutexattr_settype F
pthread_getattr_default_np F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
pthread_setattr_default_np F
GLIBC_2.2
GLIBC_2.2 A
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libpthread.abilist
index 0faa1b8..1821f67 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libpthread.abilist
@@ -10,7 +10,10 @@ GLIBC_2.12
pthread_setname_np F
GLIBC_2.18
GLIBC_2.18 A
+ __pthread_mutexattr_settype F
pthread_getattr_default_np F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
pthread_setattr_default_np F
GLIBC_2.3
GLIBC_2.3 A
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/nptl/libpthread.abilist
index 865364e..3437fde 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/nptl/libpthread.abilist
@@ -176,7 +176,10 @@ GLIBC_2.12
pthread_setname_np F
GLIBC_2.18
GLIBC_2.18 A
+ __pthread_mutexattr_settype F
pthread_getattr_default_np F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
pthread_setattr_default_np F
GLIBC_2.2
GLIBC_2.2 A
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/nptl/libpthread.abilist
index 6613c09..f69b3c8 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/nptl/libpthread.abilist
@@ -10,7 +10,10 @@ GLIBC_2.12
pthread_setname_np F
GLIBC_2.18
GLIBC_2.18 A
+ __pthread_mutexattr_settype F
pthread_getattr_default_np F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
pthread_setattr_default_np F
GLIBC_2.2
GLIBC_2.2 A
diff --git a/sysdeps/unix/sysv/linux/sh/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/sh/nptl/libpthread.abilist
index 6613c09..f69b3c8 100644
--- a/sysdeps/unix/sysv/linux/sh/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/sh/nptl/libpthread.abilist
@@ -10,7 +10,10 @@ GLIBC_2.12
pthread_setname_np F
GLIBC_2.18
GLIBC_2.18 A
+ __pthread_mutexattr_settype F
pthread_getattr_default_np F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
pthread_setattr_default_np F
GLIBC_2.2
GLIBC_2.2 A
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/nptl/libpthread.abilist
index 4c75b17..809c823 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/nptl/libpthread.abilist
@@ -176,7 +176,10 @@ GLIBC_2.12
pthread_setname_np F
GLIBC_2.18
GLIBC_2.18 A
+ __pthread_mutexattr_settype F
pthread_getattr_default_np F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
pthread_setattr_default_np F
GLIBC_2.2
GLIBC_2.2 A
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/nptl/libpthread.abilist
index a84c113..29de71d 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/nptl/libpthread.abilist
@@ -12,6 +12,9 @@ GLIBC_2.18
GLIBC_2.18 A
pthread_getattr_default_np F
pthread_setattr_default_np F
+ __pthread_mutexattr_settype F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
GLIBC_2.2
GLIBC_2.2 A
_IO_flockfile F
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/x86_64/64/nptl/libpthread.abilist
index 1b5192b..5efbc4b 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/nptl/libpthread.abilist
@@ -10,7 +10,10 @@ GLIBC_2.12
pthread_setname_np F
GLIBC_2.18
GLIBC_2.18 A
+ __pthread_mutexattr_settype F
pthread_getattr_default_np F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
pthread_setattr_default_np F
GLIBC_2.2.5
GLIBC_2.2.5 A
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/nptl/libpthread.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/nptl/libpthread.abilist
index 328f69a..7f76b19 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/nptl/libpthread.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/nptl/libpthread.abilist
@@ -224,5 +224,9 @@ GLIBC_2.16
write F
GLIBC_2.18
GLIBC_2.18 A
+ __pthread_mutexattr_settype F
pthread_getattr_default_np F
+ pthread_mutexattr_setkind_np F
+ pthread_mutexattr_settype F
pthread_setattr_default_np F
+
--
1.8.1.4