We will conditionally have a wrapper layer depending on whether the host
has the PTHREAD_SETNAME capability. It complicates stuff. Let's just
keep the wrapper there, meanwhile we opt out the pthread_setname_np()
call only. The layer can be helpful in future patches to pass data from
the parent thread to the child thread.
Signed-off-by: Peter Xu <peterx@redhat.com>
---
util/qemu-thread-posix.c | 33 +++++++++++++--------------------
1 file changed, 13 insertions(+), 20 deletions(-)
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index b789cf32e9..3ae96210d6 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -482,7 +482,6 @@ static void __attribute__((constructor)) qemu_thread_atexit_init(void)
}
-#ifdef CONFIG_PTHREAD_SETNAME_NP
typedef struct {
void *(*start_routine)(void *);
void *arg;
@@ -498,13 +497,15 @@ static void *qemu_thread_start(void *args)
/* Attempt to set the threads name; note that this is for debug, so
* we're not going to fail if we can't set it.
*/
- pthread_setname_np(pthread_self(), qemu_thread_args->name);
+#ifdef CONFIG_PTHREAD_SETNAME_NP
+ if (qemu_thread_args->name) {
+ pthread_setname_np(pthread_self(), qemu_thread_args->name);
+ }
+#endif
g_free(qemu_thread_args->name);
g_free(qemu_thread_args);
return start_routine(arg);
}
-#endif
-
void qemu_thread_create(QemuThread *thread, const char *name,
void *(*start_routine)(void*),
@@ -513,6 +514,7 @@ void qemu_thread_create(QemuThread *thread, const char *name,
sigset_t set, oldset;
int err;
pthread_attr_t attr;
+ QemuThreadArgs *qemu_thread_args;
err = pthread_attr_init(&attr);
if (err) {
@@ -527,22 +529,13 @@ void qemu_thread_create(QemuThread *thread, const char *name,
sigfillset(&set);
pthread_sigmask(SIG_SETMASK, &set, &oldset);
-#ifdef CONFIG_PTHREAD_SETNAME_NP
- if (name_threads) {
- QemuThreadArgs *qemu_thread_args;
- qemu_thread_args = g_new0(QemuThreadArgs, 1);
- qemu_thread_args->name = g_strdup(name);
- qemu_thread_args->start_routine = start_routine;
- qemu_thread_args->arg = arg;
-
- err = pthread_create(&thread->thread, &attr,
- qemu_thread_start, qemu_thread_args);
- } else
-#endif
- {
- err = pthread_create(&thread->thread, &attr,
- start_routine, arg);
- }
+ qemu_thread_args = g_new0(QemuThreadArgs, 1);
+ qemu_thread_args->name = g_strdup(name);
+ qemu_thread_args->start_routine = start_routine;
+ qemu_thread_args->arg = arg;
+
+ err = pthread_create(&thread->thread, &attr,
+ qemu_thread_start, qemu_thread_args);
if (err)
error_exit(err, __func__);
--
2.14.3
On 04/10/2018 07:49 AM, Peter Xu wrote:
> We will conditionally have a wrapper layer depending on whether the host
> has the PTHREAD_SETNAME capability. It complicates stuff. Let's just
> keep the wrapper there, meanwhile we opt out the pthread_setname_np()
> call only. The layer can be helpful in future patches to pass data from
> the parent thread to the child thread.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> util/qemu-thread-posix.c | 33 +++++++++++++--------------------
> 1 file changed, 13 insertions(+), 20 deletions(-)
>
> diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> index b789cf32e9..3ae96210d6 100644
> --- a/util/qemu-thread-posix.c
> +++ b/util/qemu-thread-posix.c
> @@ -482,7 +482,6 @@ static void __attribute__((constructor)) qemu_thread_atexit_init(void)
> }
>
More context:
static bool name_threads;
void qemu_thread_naming(bool enable)
{
name_threads = enable;
#ifndef CONFIG_THREAD_SETNAME_BYTHREAD
/* This is a debugging option, not fatal */
if (enable) {
fprintf(stderr, "qemu: thread naming not supported on this host\n");
}
#endif
}
>
> -#ifdef CONFIG_PTHREAD_SETNAME_NP
Why are we using CONFIG_THREAD_SETNAME_BYTHREAD in one place, and
CONFIG_PTHREAD_SETNAME_NP in another?
/me checks configure - oh:
# Hold two types of flag:
# CONFIG_THREAD_SETNAME_BYTHREAD - we've got a way of setting the name on
# a thread we have a handle to
# CONFIG_PTHREAD_SETNAME_NP - A way of doing it on a particular
# platform
even though, right now, we only either set both flags at once or leave
both clear, since we don't (yet?) have any other platform-specific ways
to do it.
> typedef struct {
> void *(*start_routine)(void *);
> void *arg;
> @@ -498,13 +497,15 @@ static void *qemu_thread_start(void *args)
> /* Attempt to set the threads name; note that this is for debug, so
> * we're not going to fail if we can't set it.
> */
> - pthread_setname_np(pthread_self(), qemu_thread_args->name);
> +#ifdef CONFIG_PTHREAD_SETNAME_NP
> + if (qemu_thread_args->name) {
> + pthread_setname_np(pthread_self(), qemu_thread_args->name);
Post-patch, this (attempts to) set the thread name if a non-NULL name is
present...
>
> -#ifdef CONFIG_PTHREAD_SETNAME_NP
> - if (name_threads) {
> - QemuThreadArgs *qemu_thread_args;
> - qemu_thread_args = g_new0(QemuThreadArgs, 1);
> - qemu_thread_args->name = g_strdup(name);
...but pre-patch, qemu_thread_args->name was left NULL unless
name_threads was true, because someone had called
qemu_thread_naming(true)...
> - qemu_thread_args->start_routine = start_routine;
> - qemu_thread_args->arg = arg;
> -
> - err = pthread_create(&thread->thread, &attr,
> - qemu_thread_start, qemu_thread_args);
> - } else
> -#endif
> - {
> - err = pthread_create(&thread->thread, &attr,
> - start_routine, arg);
> - }
> + qemu_thread_args = g_new0(QemuThreadArgs, 1);
> + qemu_thread_args->name = g_strdup(name);
...so you have changed semantics - you are now unconditionally trying to
set the thread name, instead of honoring qemu_thread_naming(). Do we
still need qemu_thread_naming() (tied to opt debug-threads)?
You need to either fix your code to remain conditional on whether
name_threads is set, or document the semantic change as intentional in
the commit message.
However, the idea for refactoring to always use the shim makes sense.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
On Tue, Apr 10, 2018 at 08:35:40AM -0500, Eric Blake wrote:
> On 04/10/2018 07:49 AM, Peter Xu wrote:
> > We will conditionally have a wrapper layer depending on whether the host
> > has the PTHREAD_SETNAME capability. It complicates stuff. Let's just
> > keep the wrapper there, meanwhile we opt out the pthread_setname_np()
> > call only. The layer can be helpful in future patches to pass data from
> > the parent thread to the child thread.
> >
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> > util/qemu-thread-posix.c | 33 +++++++++++++--------------------
> > 1 file changed, 13 insertions(+), 20 deletions(-)
> >
> > diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> > index b789cf32e9..3ae96210d6 100644
> > --- a/util/qemu-thread-posix.c
> > +++ b/util/qemu-thread-posix.c
> > @@ -482,7 +482,6 @@ static void __attribute__((constructor)) qemu_thread_atexit_init(void)
> > }
> >
>
> More context:
>
> static bool name_threads;
>
> void qemu_thread_naming(bool enable)
> {
> name_threads = enable;
>
> #ifndef CONFIG_THREAD_SETNAME_BYTHREAD
> /* This is a debugging option, not fatal */
> if (enable) {
> fprintf(stderr, "qemu: thread naming not supported on this host\n");
> }
> #endif
> }
>
>
> >
> > -#ifdef CONFIG_PTHREAD_SETNAME_NP
>
> Why are we using CONFIG_THREAD_SETNAME_BYTHREAD in one place, and
> CONFIG_PTHREAD_SETNAME_NP in another?
>
> /me checks configure - oh:
>
> # Hold two types of flag:
> # CONFIG_THREAD_SETNAME_BYTHREAD - we've got a way of setting the name on
> # a thread we have a handle to
> # CONFIG_PTHREAD_SETNAME_NP - A way of doing it on a particular
> # platform
>
> even though, right now, we only either set both flags at once or leave
> both clear, since we don't (yet?) have any other platform-specific ways
> to do it.
It seems so. I'm not sure whether they could be useful in the future
and I'm fine with them, hence I keep it as is.
>
> > typedef struct {
> > void *(*start_routine)(void *);
> > void *arg;
> > @@ -498,13 +497,15 @@ static void *qemu_thread_start(void *args)
> > /* Attempt to set the threads name; note that this is for debug, so
> > * we're not going to fail if we can't set it.
> > */
> > - pthread_setname_np(pthread_self(), qemu_thread_args->name);
> > +#ifdef CONFIG_PTHREAD_SETNAME_NP
> > + if (qemu_thread_args->name) {
> > + pthread_setname_np(pthread_self(), qemu_thread_args->name);
>
> Post-patch, this (attempts to) set the thread name if a non-NULL name is
> present...
>
>
> >
> > -#ifdef CONFIG_PTHREAD_SETNAME_NP
> > - if (name_threads) {
> > - QemuThreadArgs *qemu_thread_args;
> > - qemu_thread_args = g_new0(QemuThreadArgs, 1);
> > - qemu_thread_args->name = g_strdup(name);
>
> ...but pre-patch, qemu_thread_args->name was left NULL unless
> name_threads was true, because someone had called
> qemu_thread_naming(true)...
>
> > - qemu_thread_args->start_routine = start_routine;
> > - qemu_thread_args->arg = arg;
> > -
> > - err = pthread_create(&thread->thread, &attr,
> > - qemu_thread_start, qemu_thread_args);
> > - } else
> > -#endif
> > - {
> > - err = pthread_create(&thread->thread, &attr,
> > - start_routine, arg);
> > - }
> > + qemu_thread_args = g_new0(QemuThreadArgs, 1);
> > + qemu_thread_args->name = g_strdup(name);
>
> ...so you have changed semantics - you are now unconditionally trying to
> set the thread name, instead of honoring qemu_thread_naming(). Do we
> still need qemu_thread_naming() (tied to opt debug-threads)?
>
> You need to either fix your code to remain conditional on whether
> name_threads is set, or document the semantic change as intentional in
> the commit message.
Indeed, thanks for catching that. What I really wanted is probably
this:
static void *qemu_thread_start(void *args)
{
...
#ifdef CONFIG_PTHREAD_SETNAME_NP
if (name_threads && qemu_thread_args->name) {
pthread_setname_np(pthread_self(), qemu_thread_args->name);
}
#endif
...
}
I'll fix that up in next version.
>
> However, the idea for refactoring to always use the shim makes sense.
Thanks,
--
Peter Xu
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