Update.
2001-04-05 David S. Miller <davem@redhat.com> * elf/elf.h (HWCAP_SPARC_ULTRA3): Define it. * sysdeps/unix/sysv/linux/sparc/sparc32/dl-procinfo.h: Add it to capability flags table and HWCAP_IMPORTANT, increase _DL_HWCAP_COUNT to 6. * sysdeps/unix/sysv/linux/sparc/sparc64/dl-procinfo.h: Likewise.
This commit is contained in:
Ulrich Drepper
parent
8912b9aa26
commit
5e01438702
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@ -1,3 +1,11 @@
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2001-04-05 David S. Miller <davem@redhat.com>
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* elf/elf.h (HWCAP_SPARC_ULTRA3): Define it.
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* sysdeps/unix/sysv/linux/sparc/sparc32/dl-procinfo.h: Add it to
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capability flags table and HWCAP_IMPORTANT, increase
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_DL_HWCAP_COUNT to 6.
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* sysdeps/unix/sysv/linux/sparc/sparc64/dl-procinfo.h: Likewise.
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2001-04-04 David Mosberger <davidm@hpl.hp.com>
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* sysdeps/unix/sysv/linux/ia64/makecontext.c (__makecontext): Fix
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54
FAQ
54
FAQ
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@ -184,6 +184,8 @@ please let me know.
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4.8. The conversion table for character set XX does not match with
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what I expect.
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4.9. How can I find out which version of glibc I am using in the moment?
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4.10. Context switching with setcontext() does not work from within
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signal handlers.
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~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
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@ -1853,12 +1855,56 @@ int main (void) { puts (gnu_get_libc_version ()); return 0; }
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This interface can also obviously be used to perform tests at runtime if
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this should be necessary.
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4.10. Context switching with setcontext() does not work from within
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signal handlers.
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{DMT} The Linux implementations (IA-64, S390 so far) of setcontext()
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supports synchronous context switches only. There are several reasons for
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this:
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o UNIX provides no other (portable) way of effecting a synchronous
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context switch (also known as co-routine switch). Some versions
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support this via setjmp()/longjmp() but this does not work
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universally.
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o As defined by the UNIX '98 standard, the only way setcontext()
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could trigger an asychronous context switch is if this function
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were invoked on the ucontext_t pointer passed as the third argument
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to a signal handler. But according to draft 5, XPG6, XBD 2.4.3,
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setcontext() is not among the set of routines that may be called
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from a signal handler.
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o If setcontext() were to be used for asynchronous context switches,
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all kinds of synchronization and re-entrancy issues could arise and
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these problems have already been solved by real multi-threading
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libraries (e.g., POSIX threads or Linux threads).
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o Synchronous context switching can be implemented entirely in
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user-level and less state needs to be saved/restored than for an
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asynchronous context switch. It is therefore useful to distinguish
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between the two types of context switches. Indeed, some
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application vendors are known to use setcontext() to implement
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co-routines on top of normal (heavier-weight) pre-emptable threads.
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It should be noted that if someone was dead-bent on using setcontext()
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on the third arg of a signal handler, then IA-64 Linux could support
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this via a special version of sigaction() which arranges that all
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signal handlers start executing in a shim function which takes care of
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saving the preserved registers before calling the real signal handler
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and restoring them afterwards. In other words, we could provide a
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compatibility layer which would support setcontext() for asynchronous
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context switches. However, given the arguments above, I don't think
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that makes sense. setcontext() provides a decent co-routine interface
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and we should just discourage any asynchronous use (which just calls
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for trouble at any rate).
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~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
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Answers were given by:
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{UD} Ulrich Drepper, <drepper@cygnus.com>
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{DMT} David Mosberger-Tang, <davidm@AZStarNet.com>
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{UD} Ulrich Drepper, <drepper@redhat.com>
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{DMT} David Mosberger-Tang, <davidm@hpl.hp.com>
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{RM} Roland McGrath, <roland@gnu.org>
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{AJ} Andreas Jaeger, <aj@suse.de>
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{EY} Eric Youngdale, <eric@andante.jic.com>
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@ -1866,10 +1912,10 @@ Answers were given by:
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{MK} Mark Kettenis, <kettenis@phys.uva.nl>
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{ZW} Zack Weinberg, <zack@rabi.phys.columbia.edu>
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{TK} Thorsten Kukuk, <kukuk@suse.de>
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{GK} Geoffrey Keating, <geoffk@ozemail.com.au>
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{GK} Geoffrey Keating, <geoffk@redhat.com>
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{HJ} H.J. Lu, <hjl@gnu.org>
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{CG} Cristian Gafton, <gafton@redhat.com>
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{AO} Alexandre Oliva, <oliva@lsd.ic.unicamp.br>
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{AO} Alexandre Oliva, <aoliva@redhat.com>
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{BH} Bruno Haible, <haible@clisp.cons.org>
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Local Variables:
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52
FAQ.in
52
FAQ.in
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@ -1596,10 +1596,54 @@ int main (void) { puts (gnu_get_libc_version ()); return 0; }
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This interface can also obviously be used to perform tests at runtime if
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this should be necessary.
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?? Context switching with setcontext() does not work from within
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signal handlers.
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{DMT} The Linux implementations (IA-64, S390 so far) of setcontext()
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supports synchronous context switches only. There are several reasons for
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this:
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o UNIX provides no other (portable) way of effecting a synchronous
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context switch (also known as co-routine switch). Some versions
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support this via setjmp()/longjmp() but this does not work
|
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universally.
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o As defined by the UNIX '98 standard, the only way setcontext()
|
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could trigger an asychronous context switch is if this function
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were invoked on the ucontext_t pointer passed as the third argument
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to a signal handler. But according to draft 5, XPG6, XBD 2.4.3,
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setcontext() is not among the set of routines that may be called
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from a signal handler.
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o If setcontext() were to be used for asynchronous context switches,
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all kinds of synchronization and re-entrancy issues could arise and
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these problems have already been solved by real multi-threading
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libraries (e.g., POSIX threads or Linux threads).
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o Synchronous context switching can be implemented entirely in
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user-level and less state needs to be saved/restored than for an
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asynchronous context switch. It is therefore useful to distinguish
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between the two types of context switches. Indeed, some
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application vendors are known to use setcontext() to implement
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co-routines on top of normal (heavier-weight) pre-emptable threads.
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It should be noted that if someone was dead-bent on using setcontext()
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on the third arg of a signal handler, then IA-64 Linux could support
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this via a special version of sigaction() which arranges that all
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signal handlers start executing in a shim function which takes care of
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saving the preserved registers before calling the real signal handler
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and restoring them afterwards. In other words, we could provide a
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compatibility layer which would support setcontext() for asynchronous
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context switches. However, given the arguments above, I don't think
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that makes sense. setcontext() provides a decent co-routine interface
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and we should just discourage any asynchronous use (which just calls
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for trouble at any rate).
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Answers were given by:
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{UD} Ulrich Drepper, <drepper@cygnus.com>
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{DMT} David Mosberger-Tang, <davidm@AZStarNet.com>
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{UD} Ulrich Drepper, <drepper@redhat.com>
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{DMT} David Mosberger-Tang, <davidm@hpl.hp.com>
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{RM} Roland McGrath, <roland@gnu.org>
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{AJ} Andreas Jaeger, <aj@suse.de>
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{EY} Eric Youngdale, <eric@andante.jic.com>
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@ -1607,10 +1651,10 @@ Answers were given by:
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{MK} Mark Kettenis, <kettenis@phys.uva.nl>
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{ZW} Zack Weinberg, <zack@rabi.phys.columbia.edu>
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{TK} Thorsten Kukuk, <kukuk@suse.de>
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{GK} Geoffrey Keating, <geoffk@ozemail.com.au>
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{GK} Geoffrey Keating, <geoffk@redhat.com>
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{HJ} H.J. Lu, <hjl@gnu.org>
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{CG} Cristian Gafton, <gafton@redhat.com>
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{AO} Alexandre Oliva, <oliva@lsd.ic.unicamp.br>
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{AO} Alexandre Oliva, <aoliva@redhat.com>
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{BH} Bruno Haible, <haible@clisp.cons.org>
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Local Variables:
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@ -1117,6 +1117,7 @@ typedef struct
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#define HWCAP_SPARC_SWAP 4
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#define HWCAP_SPARC_MULDIV 8
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#define HWCAP_SPARC_V9 16 /* The cpu is v9, so v8plus is ok. */
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#define HWCAP_SPARC_ULTRA3 32
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/* MIPS R3000 specific definitions. */
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@ -27,9 +27,9 @@
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is still ok with the given array size. */
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static const char sparc32_cap_flags[][7] =
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{
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"flush", "stbar", "swap", "muldiv", "v9"
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"flush", "stbar", "swap", "muldiv", "v9", "ultra3"
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};
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#define _DL_HWCAP_COUNT 5
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#define _DL_HWCAP_COUNT 6
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static inline int
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__attribute__ ((unused))
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@ -68,7 +68,7 @@ _dl_string_hwcap (const char *str)
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return -1;
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};
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#define HWCAP_IMPORTANT (HWCAP_SPARC_V9)
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#define HWCAP_IMPORTANT (HWCAP_SPARC_V9|HWCAP_SPARC_ULTRA3)
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/* There are no different platforms defined. */
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#define _dl_platform_string(idx) ""
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@ -27,9 +27,9 @@
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is still ok with the given array size. */
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static const char sparc64_cap_flags[][7] =
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{
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"flush", "stbar", "swap", "muldiv", "v9"
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"flush", "stbar", "swap", "muldiv", "v9", "ultra3"
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};
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#define _DL_HWCAP_COUNT 5
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#define _DL_HWCAP_COUNT 6
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static inline int
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__attribute__ ((unused))
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@ -69,7 +69,7 @@ _dl_string_hwcap (const char *str)
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return -1;
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};
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#define HWCAP_IMPORTANT (0)
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#define HWCAP_IMPORTANT (HWCAP_SPARC_ULTRA3)
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/* There are no different platforms defined. */
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#define _dl_platform_string(idx) ""
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