[PATCH v2] add pthread_setname_np

[PATCH v2] add pthread_setname_np

[Felix Janda]

the thread name is displayed by gdb's "info threads".
---
v1->v2: add _GNU_SOURCE, and "UL" to prctl arguments

I hope that there are no programs for which this function is
performance critical...

Thanks for the review so far!
---
 include/pthread.h               |  1 +
 src/thread/pthread_setname_np.c | 26 ++++++++++++++++++++++++++
 2 files changed, 27 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..82d35e1
--- /dev/null
+++ b/src/thread/pthread_setname_np.c
@@ -0,0 +1,26 @@
+#define _GNU_SOURCE
+#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, 0UL, 0UL, 0UL) ? 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

Re: [PATCH v2] add pthread_setname_np

[Rich Felker]

On Fri, Sep 16, 2016 at 08:54:00PM -0400, Felix Janda wrote:
> the thread name is displayed by gdb's "info threads".
> ---
> v1->v2: add _GNU_SOURCE, and "UL" to prctl arguments
> 
> I hope that there are no programs for which this function is
> performance critical...
> 
> Thanks for the review so far!
> ---
>  include/pthread.h               |  1 +
>  src/thread/pthread_setname_np.c | 26 ++++++++++++++++++++++++++
>  2 files changed, 27 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..82d35e1
> --- /dev/null
> +++ b/src/thread/pthread_setname_np.c
> @@ -0,0 +1,26 @@
> +#define _GNU_SOURCE
> +#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, 0UL, 0UL, 0UL) ? 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

I don't see anything left that particularly needs changing. I'll see
if anyone else has comments and commit if not.

I did just notice that my hopes that the function could be implemented
with just public APIs aren't met, since thread->tid is needed. But
this could be fixed in the future if there's ever consensus on a
pthread_gettid_np function.

Rich

Re: [PATCH v2] add pthread_setname_np

[Rich Felker]

On Fri, Sep 16, 2016 at 08:54:00PM -0400, Felix Janda wrote:
> the thread name is displayed by gdb's "info threads".
> ---
> v1->v2: add _GNU_SOURCE, and "UL" to prctl arguments
> 
> I hope that there are no programs for which this function is
> performance critical...
> 
> Thanks for the review so far!
> ---
>  include/pthread.h               |  1 +
>  src/thread/pthread_setname_np.c | 26 ++++++++++++++++++++++++++
>  2 files changed, 27 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..82d35e1
> --- /dev/null
> +++ b/src/thread/pthread_setname_np.c
> @@ -0,0 +1,26 @@
> +#define _GNU_SOURCE
> +#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, 0UL, 0UL, 0UL) ? 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

Committed. Sorry for the delay.

Rich