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Re: cvs commit: src/sys/i386/include tls.h src/gnu/usr.bin/cc34/cc_prep/config dragonfly-spec.h src/gnu/usr.bin/cc34/cc_prep/config/i386 dragonfly.h src/lib/csu/i386 crt1.c src/lib/libc/gen tls.c src/lib/libc/i386/sys cerror.S src/lib/libc/include libc_private.h ...

From: David Xu <davidxu@xxxxxxxxxxx>
Date: Thu, 12 May 2005 09:00:28 +0800

Matthew Dillon wrote:
dillon 2005/05/11 12:47:09 PDT

DragonFly src repository

Modified files:
sys/i386/include tls.h gnu/usr.bin/cc34/cc_prep/config dragonfly-spec.h gnu/usr.bin/cc34/cc_prep/config/i386 dragonfly.h lib/csu/i386 crt1.c lib/libc/gen tls.c lib/libc/i386/sys cerror.S lib/libc/include libc_private.h lib/libc_r/uthread uthread_create.c uthread_init.c lib/libthread_xu/arch/amd64/amd64 pthread_md.c lib/libthread_xu/arch/i386/i386 pthread_md.c libexec/rtld-elf Makefile debug.h rtld.1 rtld.c rtld.h libexec/rtld-elf/i386 reloc.c rtld_machdep.h Log:
Major TLS cleanups.
* The RTLD no longer attempts to set up an initial TLS. The job has been
moved to libc. The RTLD does not use TLS itself. The
allocate_initial_tls() function has been removed.

We still have a problem not discussed yet, maybe too hurry here ? if we want to put user critical section pointer into the tcb, and used by rtld to block user signal handler, what rtld should do now ? we have deadlock problem if current thread held reader lock, and later it catches a signal and in signal handler it tries to access a __thread variable which causes additional tls data block to be allocated which needs writer lock. If rtld does not setup initial tls, then in rlock or wlock, it has to check if tls was setup or not, it will be diffcult because it does not know when libc will setup initial tls. What I am thinking is: in wlock_acquire() or rlock_acquire, rtld will access critical pointer in tcb, and use an atomic operation: struct *tcb = tls_get_tcb(); atomic_inc_int(&tcb->tcb_critical, 1); ...

in wlock_release() or rlock_release():
	atomic_inc_int(&tcb->tcb_critical, -1);
	if (tcb->tcb_critical == 0x80000000)
		getpid(); // trigger signal handler.

David Xu

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