glibc/include/sys/single_threaded.h

#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
Add the __libc_single_threaded variable The variable is placed in libc.so, and it can be true only in an outer libc, not libcs loaded via dlmopen or static dlopen. Since thread creation from inner namespaces does not work, pthread_create can update __libc_single_threaded directly. Using __libc_early_init and its initial flag, implementation of this variable is very straightforward. A future version may reset the flag during fork (but not in an inner namespace), or after joining all threads except one. Reviewed-by: DJ Delorie <dj@redhat.com> 2020-05-20 13:40:35 +00:00			`#include <misc/sys/single_threaded.h>`
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> 2022-06-07 14:11:03 +00:00
			`#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`