public inbox for glibc-cvs@sourceware.org
help / color / mirror / Atom feed
* [glibc] misc: Optimize internal usage of __libc_single_threaded
@ 2022-06-24 20:46 Adhemerval Zanella
0 siblings, 0 replies; only message in thread
From: Adhemerval Zanella @ 2022-06-24 20:46 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=baf2a265c71113a91f6971313ef191be9e77ef6a
commit baf2a265c71113a91f6971313ef191be9e77ef6a
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Tue Jun 7 11:11:03 2022 -0300
misc: Optimize internal usage of __libc_single_threaded
By adding an internal alias to avoid the GOT indirection.
On some architecture, __libc_single_thread may be accessed through
copy relocations and thus it requires to update also the copies
default copy.
This is done by adding a new internal macro,
libc_hidden_data_{proto,def}, which has an addition argument that
specifies the alias name (instead of default __GI_ one).
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Fangrui Song <maskray@google.com>
Diff:
---
elf/libc_early_init.c | 2 +-
include/libc-symbols.h | 22 ++++++++++++++++++++++
include/sys/single_threaded.h | 11 +++++++++++
misc/single_threaded.c | 2 ++
nptl/pthread_create.c | 5 ++++-
posix/fork.c | 2 +-
sysdeps/nptl/setxid.h | 2 +-
7 files changed, 42 insertions(+), 4 deletions(-)
diff --git a/elf/libc_early_init.c b/elf/libc_early_init.c
index 3c4a19cf6b..affc46fefc 100644
--- a/elf/libc_early_init.c
+++ b/elf/libc_early_init.c
@@ -38,7 +38,7 @@ __libc_early_init (_Bool initial)
__libc_single_threaded = initial;
#ifdef SHARED
- __libc_initial = initial;
+ __libc_single_threaded_internal = __libc_initial = initial;
#endif
__pthread_early_init ();
diff --git a/include/libc-symbols.h b/include/libc-symbols.h
index 4bb3d8c7ba..4fde839471 100644
--- a/include/libc-symbols.h
+++ b/include/libc-symbols.h
@@ -534,11 +534,15 @@ for linking")
__attribute__ ((visibility ("hidden"), ##attrs))
# define hidden_proto(name, attrs...) \
__hidden_proto (name, , __GI_##name, ##attrs)
+# define hidden_proto_alias(name, alias, attrs...) \
+ __hidden_proto_alias (name, , alias, ##attrs)
# define hidden_tls_proto(name, attrs...) \
__hidden_proto (name, __thread, __GI_##name, ##attrs)
# define __hidden_proto(name, thread, internal, attrs...) \
extern thread __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
__hidden_proto_hiddenattr (attrs);
+# define __hidden_proto_alias(name, thread, internal, attrs...) \
+ extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
# define __hidden_asmname(name) \
__hidden_asmname1 (__USER_LABEL_PREFIX__, name)
# define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
@@ -554,7 +558,10 @@ for linking")
# define hidden_ver(local, name) __hidden_ver1(local, __GI_##name, name);
# define hidden_data_ver(local, name) hidden_ver(local, name)
# define hidden_def(name) __hidden_ver1(__GI_##name, name, name);
+# define hidden_def_alias(name, internal) \
+ strong_alias (name, internal)
# define hidden_data_def(name) hidden_def(name)
+# define hidden_data_def_alias(name, alias) hidden_def_alias(name, alias)
# define hidden_tls_def(name) \
__hidden_ver2 (__thread, __GI_##name, name, name);
# define hidden_weak(name) \
@@ -581,9 +588,11 @@ for linking")
hidden_proto doesn't make sense for assembly but the equivalent
is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET. */
# define hidden_def(name) strong_alias (name, __GI_##name)
+# define hidden_def_alias(name, alias) strong_alias (name, alias)
# define hidden_weak(name) hidden_def (name)
# define hidden_ver(local, name) strong_alias (local, __GI_##name)
# define hidden_data_def(name) strong_data_alias (name, __GI_##name)
+# define hidden_data_def_alias(name, alias) strong_data_alias (name, alias)
# define hidden_tls_def(name) hidden_data_def (name)
# define hidden_data_weak(name) hidden_data_def (name)
# define hidden_data_ver(local, name) strong_data_alias (local, __GI_##name)
@@ -598,12 +607,17 @@ for linking")
__attribute__ ((visibility ("hidden"), ##attrs))
# define hidden_proto(name, attrs...) \
__hidden_proto (name, , name, ##attrs)
+# define hidden_proto_alias(name, alias, attrs...) \
+ __hidden_proto_alias (name, , alias, ##attrs)
# define hidden_tls_proto(name, attrs...) \
__hidden_proto (name, __thread, name, ##attrs)
# define __hidden_proto(name, thread, internal, attrs...) \
extern thread __typeof (name) name __hidden_proto_hiddenattr (attrs);
+# define __hidden_proto_alias(name, thread, internal, attrs...) \
+ extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
# else
# define hidden_proto(name, attrs...)
+# define hidden_proto_alias(name, alias, attrs...)
# define hidden_tls_proto(name, attrs...)
# endif
# else
@@ -611,9 +625,11 @@ for linking")
# endif /* Not __ASSEMBLER__ */
# define hidden_weak(name)
# define hidden_def(name)
+# define hidden_def_alias(name, alias)
# define hidden_ver(local, name)
# define hidden_data_weak(name)
# define hidden_data_def(name)
+# define hidden_data_def_alias(name, alias)
# define hidden_tls_def(name)
# define hidden_data_ver(local, name)
# define hidden_nolink(name, lib, version)
@@ -621,22 +637,28 @@ for linking")
#if IS_IN (libc)
# define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
+# define libc_hidden_proto_alias(name, alias, attrs...) \
+ hidden_proto_alias (name, alias, ##attrs)
# define libc_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
# define libc_hidden_def(name) hidden_def (name)
+# define libc_hidden_def_alias(name, alias) hidden_def_alias (name, alias)
# define libc_hidden_weak(name) hidden_weak (name)
# define libc_hidden_nolink_sunrpc(name, version) hidden_nolink (name, libc, version)
# define libc_hidden_ver(local, name) hidden_ver (local, name)
# define libc_hidden_data_def(name) hidden_data_def (name)
+# define libc_hidden_data_def_alias(name, alias) hidden_data_def_alias (name, alias)
# define libc_hidden_tls_def(name) hidden_tls_def (name)
# define libc_hidden_data_weak(name) hidden_data_weak (name)
# define libc_hidden_data_ver(local, name) hidden_data_ver (local, name)
#else
# define libc_hidden_proto(name, attrs...)
+# define libc_hidden_proto_alias(name, alias, attrs...)
# define libc_hidden_tls_proto(name, attrs...)
# define libc_hidden_def(name)
# define libc_hidden_weak(name)
# define libc_hidden_ver(local, name)
# define libc_hidden_data_def(name)
+# define libc_hidden_data_def_alias(name, alias)
# define libc_hidden_tls_def(name)
# define libc_hidden_data_weak(name)
# define libc_hidden_data_ver(local, name)
diff --git a/include/sys/single_threaded.h b/include/sys/single_threaded.h
index 18f6972482..2015742be0 100644
--- a/include/sys/single_threaded.h
+++ b/include/sys/single_threaded.h
@@ -1 +1,12 @@
#include <misc/sys/single_threaded.h>
+
+#ifndef _ISOMAC
+
+libc_hidden_proto_alias (__libc_single_threaded,
+ __libc_single_threaded_internal);
+
+#if !defined SHARED || !IS_IN(libc)
+# define __libc_single_threaded_internal __libc_single_threaded
+#endif
+
+#endif
diff --git a/misc/single_threaded.c b/misc/single_threaded.c
index 96ada9137b..9b0746a69c 100644
--- a/misc/single_threaded.c
+++ b/misc/single_threaded.c
@@ -25,3 +25,5 @@ char __libc_single_threaded;
#else
char __libc_single_threaded = 1;
#endif
+libc_hidden_data_def_alias (__libc_single_threaded,
+ __libc_single_threaded_internal)
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index e7a099acb7..a06d611e32 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -624,9 +624,12 @@ __pthread_create_2_1 (pthread_t *newthread, const pthread_attr_t *attr,
/* Avoid a data race in the multi-threaded case, and call the
deferred initialization only once. */
- if (__libc_single_threaded)
+ if (__libc_single_threaded_internal)
{
late_init ();
+ __libc_single_threaded_internal = 0;
+ /* __libc_single_threaded can be accessed through copy relocations, so
+ it requires to update the external copy. */
__libc_single_threaded = 0;
}
diff --git a/posix/fork.c b/posix/fork.c
index e1be3422ea..987916a175 100644
--- a/posix/fork.c
+++ b/posix/fork.c
@@ -45,7 +45,7 @@ __libc_fork (void)
requirement for fork (Austin Group tracker issue #62) this is
best effort to make is async-signal-safe at least for single-thread
case. */
- bool multiple_threads = __libc_single_threaded == 0;
+ bool multiple_threads = __libc_single_threaded_internal == 0;
uint64_t lastrun;
lastrun = __run_prefork_handlers (multiple_threads);
diff --git a/sysdeps/nptl/setxid.h b/sysdeps/nptl/setxid.h
index b821d6bc07..b87cad7b18 100644
--- a/sysdeps/nptl/setxid.h
+++ b/sysdeps/nptl/setxid.h
@@ -29,7 +29,7 @@
#define INLINE_SETXID_SYSCALL(name, nr, args...) \
({ \
int __result; \
- if (!__libc_single_threaded) \
+ if (!__libc_single_threaded_internal) \
{ \
struct xid_command __cmd; \
__cmd.syscall_no = __NR_##name; \
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2022-06-24 20:46 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-06-24 20:46 [glibc] misc: Optimize internal usage of __libc_single_threaded Adhemerval Zanella
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).