* [PATCH] add pthread_setname_np
@ 2016-09-16 0:23 Felix Janda
2016-09-16 9:03 ` Alexander Monakov
0 siblings, 1 reply; 4+ messages in thread
From: Felix Janda @ 2016-09-16 0:23 UTC (permalink / raw)
To: musl
the thread name can be displayed using gdb's "info threads".
---
include/pthread.h | 1 +
src/thread/pthread_setname_np.c | 25 +++++++++++++++++++++++++
2 files changed, 26 insertions(+)
create mode 100644 src/thread/pthread_setname_np.c
diff --git a/include/pthread.h b/include/pthread.h
index 3d2e0c4..94ef919 100644
--- a/include/pthread.h
+++ b/include/pthread.h
@@ -214,6 +214,7 @@ struct cpu_set_t;
int pthread_getaffinity_np(pthread_t, size_t, struct cpu_set_t *);
int pthread_setaffinity_np(pthread_t, size_t, const struct cpu_set_t *);
int pthread_getattr_np(pthread_t, pthread_attr_t *);
+int pthread_setname_np(pthread_t, const char *);
int pthread_tryjoin_np(pthread_t, void **);
int pthread_timedjoin_np(pthread_t, void **, const struct timespec *);
#endif
diff --git a/src/thread/pthread_setname_np.c b/src/thread/pthread_setname_np.c
new file mode 100644
index 0000000..e328c0d
--- /dev/null
+++ b/src/thread/pthread_setname_np.c
@@ -0,0 +1,25 @@
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/prctl.h>
+
+#include "pthread_impl.h"
+
+int pthread_setname_np(pthread_t thread, const char *name)
+{
+ int fd, cs, status = 0;
+ char f[sizeof "/proc/self/task//comm" + 3*sizeof(int)];
+ size_t len;
+
+ if ((len = strnlen(name, 16)) > 15) return ERANGE;
+
+ if (thread == pthread_self())
+ return prctl(PR_SET_NAME, (unsigned long)name, 0, 0, 0) ? errno : 0;
+
+ snprintf(f, sizeof f, "/proc/self/task/%d/comm", thread->tid);
+ pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+ if ((fd = open(f, O_WRONLY)) < 0 || write(fd, name, len) < 0) status = errno;
+ if (fd >= 0) close(fd);
+ pthread_setcancelstate(cs, 0);
+ return status;
+}
--
2.7.3
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] add pthread_setname_np
2016-09-16 0:23 [PATCH] add pthread_setname_np Felix Janda
@ 2016-09-16 9:03 ` Alexander Monakov
2016-09-16 9:09 ` Alexander Monakov
2016-09-16 15:00 ` Rich Felker
0 siblings, 2 replies; 4+ messages in thread
From: Alexander Monakov @ 2016-09-16 9:03 UTC (permalink / raw)
To: musl
Hi,
On Thu, 15 Sep 2016, Felix Janda wrote:
> --- /dev/null
> +++ b/src/thread/pthread_setname_np.c
> @@ -0,0 +1,25 @@
> +#include <fcntl.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <sys/prctl.h>
> +
> +#include "pthread_impl.h"
This should bring in the declaration of pthread_setname_np from pthread.h by
#defin'ing _GNU_SOURCE prior to inclusion.
(today, this rule is not enforced with warnings and thus not always followed in
musl, for example the recent pthread_tryjoin_np patch missed that as well)
> +int pthread_setname_np(pthread_t thread, const char *name)
> +{
> + int fd, cs, status = 0;
> + char f[sizeof "/proc/self/task//comm" + 3*sizeof(int)];
> + size_t len;
> +
> + if ((len = strnlen(name, 16)) > 15) return ERANGE;
> +
> + if (thread == pthread_self())
This likely should use the static inline function __pthread_self()?
> + return prctl(PR_SET_NAME, (unsigned long)name, 0, 0, 0) ? errno : 0;
First, prctl is declared as a variadic function, so zeros should be passed with
the right type (0ul); passing fewer than 5 arguments will cause musl's
implementation of prctl to invoke UB, since it always retrieves 4 variadic arguments.
Second, while I don't have a strong opinion on whether musl wants to use prctl
here (my previous comment in this thread was based on the wrong idea that prctl
would be sufficient in all cases - sorry about that), I think some tuning would
be nice in case the decision is to use prctl. So, either
return -__syscall(SYS_prctl, PR_SET_NAME, name);
(not sure if Rich would like it), or
if (thread == pthread_self()) {
status = prctl(...);
} else {
...
fd = status = open(f, O_WRONLY);
if (fd >= 0) {
status = write(fd, name, len);
close(fd);
}
pthread_setcancelstate(cs, 0);
}
return status ? errno : 0;
> + snprintf(f, sizeof f, "/proc/self/task/%d/comm", thread->tid);
> + pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
> + if ((fd = open(f, O_WRONLY)) < 0 || write(fd, name, len) < 0) status = errno;
> + if (fd >= 0) close(fd);
> + pthread_setcancelstate(cs, 0);
> + return status;
> +}
Thanks.
Alexander
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] add pthread_setname_np
2016-09-16 9:03 ` Alexander Monakov
@ 2016-09-16 9:09 ` Alexander Monakov
2016-09-16 15:00 ` Rich Felker
1 sibling, 0 replies; 4+ messages in thread
From: Alexander Monakov @ 2016-09-16 9:09 UTC (permalink / raw)
To: musl
On Fri, 16 Sep 2016, Alexander Monakov wrote:
> return status ? errno : 0;
status < 0 ? errno : 0
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] add pthread_setname_np
2016-09-16 9:03 ` Alexander Monakov
2016-09-16 9:09 ` Alexander Monakov
@ 2016-09-16 15:00 ` Rich Felker
1 sibling, 0 replies; 4+ messages in thread
From: Rich Felker @ 2016-09-16 15:00 UTC (permalink / raw)
To: musl
On Fri, Sep 16, 2016 at 12:03:16PM +0300, Alexander Monakov wrote:
> Hi,
>
> On Thu, 15 Sep 2016, Felix Janda wrote:
> > --- /dev/null
> > +++ b/src/thread/pthread_setname_np.c
> > @@ -0,0 +1,25 @@
> > +#include <fcntl.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +#include <sys/prctl.h>
> > +
> > +#include "pthread_impl.h"
>
> This should bring in the declaration of pthread_setname_np from pthread.h by
> #defin'ing _GNU_SOURCE prior to inclusion.
> (today, this rule is not enforced with warnings and thus not always followed in
> musl, for example the recent pthread_tryjoin_np patch missed that as well)
Yep.
> > +int pthread_setname_np(pthread_t thread, const char *name)
> > +{
> > + int fd, cs, status = 0;
> > + char f[sizeof "/proc/self/task//comm" + 3*sizeof(int)];
> > + size_t len;
> > +
> > + if ((len = strnlen(name, 16)) > 15) return ERANGE;
> > +
> > + if (thread == pthread_self())
>
> This likely should use the static inline function __pthread_self()?
My preference when implementing nonstandard extension/junk functions
that are not performance-critical is to write them using nothing but
public APIs so that they're musl-agnostic and thereby
maintenance-free. Certainly saving a few bytes/cycles for the function
call here is not worthwhile so I'd stick with pthread_self().
> > + return prctl(PR_SET_NAME, (unsigned long)name, 0, 0, 0) ? errno : 0;
>
> First, prctl is declared as a variadic function, so zeros should be passed with
> the right type (0ul); passing fewer than 5 arguments will cause musl's
> implementation of prctl to invoke UB, since it always retrieves 4 variadic arguments.
>
> Second, while I don't have a strong opinion on whether musl wants to use prctl
> here (my previous comment in this thread was based on the wrong idea that prctl
> would be sufficient in all cases - sorry about that), I think some tuning would
> be nice in case the decision is to use prctl. So, either
>
> return -__syscall(SYS_prctl, PR_SET_NAME, name);
>
> (not sure if Rich would like it), or
See above. This would be smaller but if we (or someone else using the
code) wanted to change the conventions of how __syscall is used, this
would require them to dig info nonstandard functions (which don't
_need_ to be using __syscall) in addition to all the standard ones
(which might need to do this for namespace reasons, etc.). So I'd
prefer just using the public interface.
> if (thread == pthread_self()) {
> status = prctl(...);
> } else {
> ...
> fd = status = open(f, O_WRONLY);
> if (fd >= 0) {
> status = write(fd, name, len);
> close(fd);
> }
> pthread_setcancelstate(cs, 0);
> }
> return status ? errno : 0;
>
> > + snprintf(f, sizeof f, "/proc/self/task/%d/comm", thread->tid);
> > + pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
> > + if ((fd = open(f, O_WRONLY)) < 0 || write(fd, name, len) < 0) status = errno;
> > + if (fd >= 0) close(fd);
> > + pthread_setcancelstate(cs, 0);
> > + return status;
> > +}
I don't have a strong opinion on how this part is structured.
Rich
^ permalink raw reply [flat|nested] 4+ messages in thread
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2016-09-16 0:23 [PATCH] add pthread_setname_np Felix Janda
2016-09-16 9:03 ` Alexander Monakov
2016-09-16 9:09 ` Alexander Monakov
2016-09-16 15:00 ` Rich Felker
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