| Message ID | 1454083668-23520-1-git-send-email-stefanha@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Stefan Hajnoczi <stefanha@redhat.com> writes: > The GThread coroutine backend was a portable coroutine implementation. > Over the years all platforms got their own optimized coroutine > implementations and nothing uses the GThread backend anymore. > > In fact, ./configure mentions the GThread backend doesn't work but might > be useful for debugging. Since GDB macros were added to ease debugging > of ucontext coroutines, there seems little point in keeping a broken > backend around. Except I found that I couldn't run the ThreadSanitizer without using the gthread co-routines. So while I totally agree we should dump stuff that's not used lets make sure no one else relies on it for debugging stuff as well. > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > configure | 19 ++--- > util/coroutine-gthread.c | 198 ----------------------------------------------- > 2 files changed, 5 insertions(+), 212 deletions(-) > delete mode 100644 util/coroutine-gthread.c > > diff --git a/configure b/configure > index 3506e44..789fd7d 100755 > --- a/configure > +++ b/configure > @@ -1322,7 +1322,7 @@ Advanced options (experts only): > --oss-lib path to OSS library > --cpu=CPU Build for host CPU [$cpu] > --with-coroutine=BACKEND coroutine backend. Supported options: > - gthread, ucontext, sigaltstack, windows > + ucontext, sigaltstack, windows > --enable-gcov enable test coverage analysis with gcov > --gcov=GCOV use specified gcov [$gcov_tool] > --disable-blobs disable installing provided firmware blobs > @@ -4314,10 +4314,8 @@ fi > # check and set a backend for coroutine > > # We prefer ucontext, but it's not always possible. The fallback > -# is sigcontext. gthread is not selectable except explicitly, because > -# it is not functional enough to run QEMU proper. (It is occasionally > -# useful for debugging purposes.) On Windows the only valid backend > -# is the Windows-specific one. > +# is sigcontext. On Windows the only valid backend is the Windows-specific > +# one. > > ucontext_works=no > if test "$darwin" != "yes"; then > @@ -4356,7 +4354,7 @@ else > feature_not_found "ucontext" > fi > ;; > - gthread|sigaltstack) > + sigaltstack) > if test "$mingw32" = "yes"; then > error_exit "only the 'windows' coroutine backend is valid for Windows" > fi > @@ -4368,14 +4366,7 @@ else > fi > > if test "$coroutine_pool" = ""; then > - if test "$coroutine" = "gthread"; then > - coroutine_pool=no > - else > - coroutine_pool=yes > - fi > -fi > -if test "$coroutine" = "gthread" -a "$coroutine_pool" = "yes"; then > - error_exit "'gthread' coroutine backend does not support pool (use --disable-coroutine-pool)" > + coroutine_pool=yes > fi > > ########################################## > diff --git a/util/coroutine-gthread.c b/util/coroutine-gthread.c > deleted file mode 100644 > index 0bcd778..0000000 > --- a/util/coroutine-gthread.c > +++ /dev/null > @@ -1,198 +0,0 @@ > -/* > - * GThread coroutine initialization code > - * > - * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws> > - * Copyright (C) 2011 Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> > - * > - * This library is free software; you can redistribute it and/or > - * modify it under the terms of the GNU Lesser General Public > - * License as published by the Free Software Foundation; either > - * version 2.0 of the License, or (at your option) any later version. > - * > - * This library is distributed in the hope that it will be useful, > - * but WITHOUT ANY WARRANTY; without even the implied warranty of > - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > - * Lesser General Public License for more details. > - * > - * You should have received a copy of the GNU Lesser General Public > - * License along with this library; if not, see <http://www.gnu.org/licenses/>. > - */ > - > -#include <glib.h> > -#include "qemu-common.h" > -#include "qemu/coroutine_int.h" > - > -typedef struct { > - Coroutine base; > - GThread *thread; > - bool runnable; > - bool free_on_thread_exit; > - CoroutineAction action; > -} CoroutineGThread; > - > -static CompatGMutex coroutine_lock; > -static CompatGCond coroutine_cond; > - > -/* GLib 2.31 and beyond deprecated various parts of the thread API, > - * but the new interfaces are not available in older GLib versions > - * so we have to cope with both. > - */ > -#if GLIB_CHECK_VERSION(2, 31, 0) > -/* Awkwardly, the GPrivate API doesn't provide a way to update the > - * GDestroyNotify handler for the coroutine key dynamically. So instead > - * we track whether or not the CoroutineGThread should be freed on > - * thread exit / coroutine key update using the free_on_thread_exit > - * field. > - */ > -static void coroutine_destroy_notify(gpointer data) > -{ > - CoroutineGThread *co = data; > - if (co && co->free_on_thread_exit) { > - g_free(co); > - } > -} > - > -static GPrivate coroutine_key = G_PRIVATE_INIT(coroutine_destroy_notify); > - > -static inline CoroutineGThread *get_coroutine_key(void) > -{ > - return g_private_get(&coroutine_key); > -} > - > -static inline void set_coroutine_key(CoroutineGThread *co, > - bool free_on_thread_exit) > -{ > - /* Unlike g_static_private_set() this does not call the GDestroyNotify > - * if the previous value of the key was NULL. Fortunately we only need > - * the GDestroyNotify in the non-NULL key case. > - */ > - co->free_on_thread_exit = free_on_thread_exit; > - g_private_replace(&coroutine_key, co); > -} > - > -static inline GThread *create_thread(GThreadFunc func, gpointer data) > -{ > - return g_thread_new("coroutine", func, data); > -} > - > -#else > - > -/* Handle older GLib versions */ > - > -static GStaticPrivate coroutine_key = G_STATIC_PRIVATE_INIT; > - > -static inline CoroutineGThread *get_coroutine_key(void) > -{ > - return g_static_private_get(&coroutine_key); > -} > - > -static inline void set_coroutine_key(CoroutineGThread *co, > - bool free_on_thread_exit) > -{ > - g_static_private_set(&coroutine_key, co, > - free_on_thread_exit ? (GDestroyNotify)g_free : NULL); > -} > - > -static inline GThread *create_thread(GThreadFunc func, gpointer data) > -{ > - return g_thread_create_full(func, data, 0, TRUE, TRUE, > - G_THREAD_PRIORITY_NORMAL, NULL); > -} > - > -#endif > - > - > -static void __attribute__((constructor)) coroutine_init(void) > -{ > -#if !GLIB_CHECK_VERSION(2, 31, 0) > - if (!g_thread_supported()) { > - g_thread_init(NULL); > - } > -#endif > -} > - > -static void coroutine_wait_runnable_locked(CoroutineGThread *co) > -{ > - while (!co->runnable) { > - g_cond_wait(&coroutine_cond, &coroutine_lock); > - } > -} > - > -static void coroutine_wait_runnable(CoroutineGThread *co) > -{ > - g_mutex_lock(&coroutine_lock); > - coroutine_wait_runnable_locked(co); > - g_mutex_unlock(&coroutine_lock); > -} > - > -static gpointer coroutine_thread(gpointer opaque) > -{ > - CoroutineGThread *co = opaque; > - > - set_coroutine_key(co, false); > - coroutine_wait_runnable(co); > - co->base.entry(co->base.entry_arg); > - qemu_coroutine_switch(&co->base, co->base.caller, COROUTINE_TERMINATE); > - return NULL; > -} > - > -Coroutine *qemu_coroutine_new(void) > -{ > - CoroutineGThread *co; > - > - co = g_malloc0(sizeof(*co)); > - co->thread = create_thread(coroutine_thread, co); > - if (!co->thread) { > - g_free(co); > - return NULL; > - } > - return &co->base; > -} > - > -void qemu_coroutine_delete(Coroutine *co_) > -{ > - CoroutineGThread *co = DO_UPCAST(CoroutineGThread, base, co_); > - > - g_thread_join(co->thread); > - g_free(co); > -} > - > -CoroutineAction qemu_coroutine_switch(Coroutine *from_, > - Coroutine *to_, > - CoroutineAction action) > -{ > - CoroutineGThread *from = DO_UPCAST(CoroutineGThread, base, from_); > - CoroutineGThread *to = DO_UPCAST(CoroutineGThread, base, to_); > - > - g_mutex_lock(&coroutine_lock); > - from->runnable = false; > - from->action = action; > - to->runnable = true; > - to->action = action; > - g_cond_broadcast(&coroutine_cond); > - > - if (action != COROUTINE_TERMINATE) { > - coroutine_wait_runnable_locked(from); > - } > - g_mutex_unlock(&coroutine_lock); > - return from->action; > -} > - > -Coroutine *qemu_coroutine_self(void) > -{ > - CoroutineGThread *co = get_coroutine_key(); > - if (!co) { > - co = g_malloc0(sizeof(*co)); > - co->runnable = true; > - set_coroutine_key(co, true); > - } > - > - return &co->base; > -} > - > -bool qemu_in_coroutine(void) > -{ > - CoroutineGThread *co = get_coroutine_key(); > - > - return co && co->base.caller; > -} -- Alex Bennée
On Fri, Jan 29, 2016 at 04:41:41PM +0000, Alex Bennée wrote: > > Stefan Hajnoczi <stefanha@redhat.com> writes: > > > The GThread coroutine backend was a portable coroutine implementation. > > Over the years all platforms got their own optimized coroutine > > implementations and nothing uses the GThread backend anymore. > > > > In fact, ./configure mentions the GThread backend doesn't work but might > > be useful for debugging. Since GDB macros were added to ease debugging > > of ucontext coroutines, there seems little point in keeping a broken > > backend around. > > Except I found that I couldn't run the ThreadSanitizer without using the > gthread co-routines. So while I totally agree we should dump stuff > that's not used lets make sure no one else relies on it for debugging > stuff as well. Is it still the case that ThreadSanitizer only works with gthread coroutines? Stefan
Stefan Hajnoczi <stefanha@redhat.com> writes: > On Fri, Jan 29, 2016 at 04:41:41PM +0000, Alex Bennée wrote: >> >> Stefan Hajnoczi <stefanha@redhat.com> writes: >> >> > The GThread coroutine backend was a portable coroutine implementation. >> > Over the years all platforms got their own optimized coroutine >> > implementations and nothing uses the GThread backend anymore. >> > >> > In fact, ./configure mentions the GThread backend doesn't work but might >> > be useful for debugging. Since GDB macros were added to ease debugging >> > of ucontext coroutines, there seems little point in keeping a broken >> > backend around. >> >> Except I found that I couldn't run the ThreadSanitizer without using the >> gthread co-routines. So while I totally agree we should dump stuff >> that's not used lets make sure no one else relies on it for debugging >> stuff as well. > > Is it still the case that ThreadSanitizer only works with gthread > coroutines? It certainly was very confused about what was going on with the default option (sigucontext IIRC?). > > Stefan -- Alex Bennée
On Mon, Feb 01, 2016 at 12:17:14PM +0000, Alex Bennée wrote: > > Stefan Hajnoczi <stefanha@redhat.com> writes: > > > On Fri, Jan 29, 2016 at 04:41:41PM +0000, Alex Bennée wrote: > >> > >> Stefan Hajnoczi <stefanha@redhat.com> writes: > >> > >> > The GThread coroutine backend was a portable coroutine implementation. > >> > Over the years all platforms got their own optimized coroutine > >> > implementations and nothing uses the GThread backend anymore. > >> > > >> > In fact, ./configure mentions the GThread backend doesn't work but might > >> > be useful for debugging. Since GDB macros were added to ease debugging > >> > of ucontext coroutines, there seems little point in keeping a broken > >> > backend around. > >> > >> Except I found that I couldn't run the ThreadSanitizer without using the > >> gthread co-routines. So while I totally agree we should dump stuff > >> that's not used lets make sure no one else relies on it for debugging > >> stuff as well. > > > > Is it still the case that ThreadSanitizer only works with gthread > > coroutines? > > It certainly was very confused about what was going on with the default > option (sigucontext IIRC?). Okay, it looks like there is a good reason to keep the GThread backend. If I have time I'd like to look into the reason why the GThread backend doesn't pass "make check". I noticed that ide tests were hanging. Stefan
On Fri, Jan 29, 2016 at 04:07:48PM +0000, Stefan Hajnoczi wrote: > The GThread coroutine backend was a portable coroutine implementation. > Over the years all platforms got their own optimized coroutine > implementations and nothing uses the GThread backend anymore. > > In fact, ./configure mentions the GThread backend doesn't work but might > be useful for debugging. Since GDB macros were added to ease debugging > of ucontext coroutines, there seems little point in keeping a broken > backend around. > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > configure | 19 ++--- > util/coroutine-gthread.c | 198 ----------------------------------------------- > 2 files changed, 5 insertions(+), 212 deletions(-) > delete mode 100644 util/coroutine-gthread.c NACK Alex Bennee pointed out that ThreadSanitizer needs the GThread backend because it cannot cope with stack switching. Stefan
diff --git a/configure b/configure index 3506e44..789fd7d 100755 --- a/configure +++ b/configure @@ -1322,7 +1322,7 @@ Advanced options (experts only): --oss-lib path to OSS library --cpu=CPU Build for host CPU [$cpu] --with-coroutine=BACKEND coroutine backend. Supported options: - gthread, ucontext, sigaltstack, windows + ucontext, sigaltstack, windows --enable-gcov enable test coverage analysis with gcov --gcov=GCOV use specified gcov [$gcov_tool] --disable-blobs disable installing provided firmware blobs @@ -4314,10 +4314,8 @@ fi # check and set a backend for coroutine # We prefer ucontext, but it's not always possible. The fallback -# is sigcontext. gthread is not selectable except explicitly, because -# it is not functional enough to run QEMU proper. (It is occasionally -# useful for debugging purposes.) On Windows the only valid backend -# is the Windows-specific one. +# is sigcontext. On Windows the only valid backend is the Windows-specific +# one. ucontext_works=no if test "$darwin" != "yes"; then @@ -4356,7 +4354,7 @@ else feature_not_found "ucontext" fi ;; - gthread|sigaltstack) + sigaltstack) if test "$mingw32" = "yes"; then error_exit "only the 'windows' coroutine backend is valid for Windows" fi @@ -4368,14 +4366,7 @@ else fi if test "$coroutine_pool" = ""; then - if test "$coroutine" = "gthread"; then - coroutine_pool=no - else - coroutine_pool=yes - fi -fi -if test "$coroutine" = "gthread" -a "$coroutine_pool" = "yes"; then - error_exit "'gthread' coroutine backend does not support pool (use --disable-coroutine-pool)" + coroutine_pool=yes fi ########################################## diff --git a/util/coroutine-gthread.c b/util/coroutine-gthread.c deleted file mode 100644 index 0bcd778..0000000 --- a/util/coroutine-gthread.c +++ /dev/null @@ -1,198 +0,0 @@ -/* - * GThread coroutine initialization code - * - * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws> - * Copyright (C) 2011 Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> - * - * This library is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public - * License as published by the Free Software Foundation; either - * version 2.0 of the License, or (at your option) any later version. - * - * This library is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this library; if not, see <http://www.gnu.org/licenses/>. - */ - -#include <glib.h> -#include "qemu-common.h" -#include "qemu/coroutine_int.h" - -typedef struct { - Coroutine base; - GThread *thread; - bool runnable; - bool free_on_thread_exit; - CoroutineAction action; -} CoroutineGThread; - -static CompatGMutex coroutine_lock; -static CompatGCond coroutine_cond; - -/* GLib 2.31 and beyond deprecated various parts of the thread API, - * but the new interfaces are not available in older GLib versions - * so we have to cope with both. - */ -#if GLIB_CHECK_VERSION(2, 31, 0) -/* Awkwardly, the GPrivate API doesn't provide a way to update the - * GDestroyNotify handler for the coroutine key dynamically. So instead - * we track whether or not the CoroutineGThread should be freed on - * thread exit / coroutine key update using the free_on_thread_exit - * field. - */ -static void coroutine_destroy_notify(gpointer data) -{ - CoroutineGThread *co = data; - if (co && co->free_on_thread_exit) { - g_free(co); - } -} - -static GPrivate coroutine_key = G_PRIVATE_INIT(coroutine_destroy_notify); - -static inline CoroutineGThread *get_coroutine_key(void) -{ - return g_private_get(&coroutine_key); -} - -static inline void set_coroutine_key(CoroutineGThread *co, - bool free_on_thread_exit) -{ - /* Unlike g_static_private_set() this does not call the GDestroyNotify - * if the previous value of the key was NULL. Fortunately we only need - * the GDestroyNotify in the non-NULL key case. - */ - co->free_on_thread_exit = free_on_thread_exit; - g_private_replace(&coroutine_key, co); -} - -static inline GThread *create_thread(GThreadFunc func, gpointer data) -{ - return g_thread_new("coroutine", func, data); -} - -#else - -/* Handle older GLib versions */ - -static GStaticPrivate coroutine_key = G_STATIC_PRIVATE_INIT; - -static inline CoroutineGThread *get_coroutine_key(void) -{ - return g_static_private_get(&coroutine_key); -} - -static inline void set_coroutine_key(CoroutineGThread *co, - bool free_on_thread_exit) -{ - g_static_private_set(&coroutine_key, co, - free_on_thread_exit ? (GDestroyNotify)g_free : NULL); -} - -static inline GThread *create_thread(GThreadFunc func, gpointer data) -{ - return g_thread_create_full(func, data, 0, TRUE, TRUE, - G_THREAD_PRIORITY_NORMAL, NULL); -} - -#endif - - -static void __attribute__((constructor)) coroutine_init(void) -{ -#if !GLIB_CHECK_VERSION(2, 31, 0) - if (!g_thread_supported()) { - g_thread_init(NULL); - } -#endif -} - -static void coroutine_wait_runnable_locked(CoroutineGThread *co) -{ - while (!co->runnable) { - g_cond_wait(&coroutine_cond, &coroutine_lock); - } -} - -static void coroutine_wait_runnable(CoroutineGThread *co) -{ - g_mutex_lock(&coroutine_lock); - coroutine_wait_runnable_locked(co); - g_mutex_unlock(&coroutine_lock); -} - -static gpointer coroutine_thread(gpointer opaque) -{ - CoroutineGThread *co = opaque; - - set_coroutine_key(co, false); - coroutine_wait_runnable(co); - co->base.entry(co->base.entry_arg); - qemu_coroutine_switch(&co->base, co->base.caller, COROUTINE_TERMINATE); - return NULL; -} - -Coroutine *qemu_coroutine_new(void) -{ - CoroutineGThread *co; - - co = g_malloc0(sizeof(*co)); - co->thread = create_thread(coroutine_thread, co); - if (!co->thread) { - g_free(co); - return NULL; - } - return &co->base; -} - -void qemu_coroutine_delete(Coroutine *co_) -{ - CoroutineGThread *co = DO_UPCAST(CoroutineGThread, base, co_); - - g_thread_join(co->thread); - g_free(co); -} - -CoroutineAction qemu_coroutine_switch(Coroutine *from_, - Coroutine *to_, - CoroutineAction action) -{ - CoroutineGThread *from = DO_UPCAST(CoroutineGThread, base, from_); - CoroutineGThread *to = DO_UPCAST(CoroutineGThread, base, to_); - - g_mutex_lock(&coroutine_lock); - from->runnable = false; - from->action = action; - to->runnable = true; - to->action = action; - g_cond_broadcast(&coroutine_cond); - - if (action != COROUTINE_TERMINATE) { - coroutine_wait_runnable_locked(from); - } - g_mutex_unlock(&coroutine_lock); - return from->action; -} - -Coroutine *qemu_coroutine_self(void) -{ - CoroutineGThread *co = get_coroutine_key(); - if (!co) { - co = g_malloc0(sizeof(*co)); - co->runnable = true; - set_coroutine_key(co, true); - } - - return &co->base; -} - -bool qemu_in_coroutine(void) -{ - CoroutineGThread *co = get_coroutine_key(); - - return co && co->base.caller; -}
The GThread coroutine backend was a portable coroutine implementation. Over the years all platforms got their own optimized coroutine implementations and nothing uses the GThread backend anymore. In fact, ./configure mentions the GThread backend doesn't work but might be useful for debugging. Since GDB macros were added to ease debugging of ucontext coroutines, there seems little point in keeping a broken backend around. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- configure | 19 ++--- util/coroutine-gthread.c | 198 ----------------------------------------------- 2 files changed, 5 insertions(+), 212 deletions(-) delete mode 100644 util/coroutine-gthread.c