* [PATCH RFC] add pthread_setname_np
@ 2016-09-15 3:02 Felix Janda
2016-09-15 3:27 ` Rich Felker
2016-09-15 6:32 ` Alexander Monakov
0 siblings, 2 replies; 8+ messages in thread
From: Felix Janda @ 2016-09-15 3:02 UTC (permalink / raw)
To: musl
gdb's "info threads" displays the thread name.
---
Should this function care about interrupted syscalls?
---
include/pthread.h | 1 +
src/thread/pthread_setname_np.c | 21 +++++++++++++++++++++
2 files changed, 22 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..b7f7a4b
--- /dev/null
+++ b/src/thread/pthread_setname_np.c
@@ -0,0 +1,21 @@
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "pthread_impl.h"
+
+int pthread_setname_np(pthread_t thread, const char *name)
+{
+ int fd, status = 0;
+ char f[sizeof "/proc/self/task//comm" + 7];
+ ssize_t len;
+
+ if ((len = strlen(name)) > 15) return ERANGE;
+
+ snprintf(f, sizeof f, "/proc/self/task/%d/comm", thread->tid);
+ if ((fd = open(f, O_WRONLY)) < 0) return errno;
+ if (write(fd, name, len) < 0) status = errno;
+
+ close(fd);
+ return status;
+}
--
2.7.3
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH RFC] add pthread_setname_np
2016-09-15 3:02 [PATCH RFC] add pthread_setname_np Felix Janda
@ 2016-09-15 3:27 ` Rich Felker
2016-09-15 3:43 ` Felix Janda
2016-09-15 6:32 ` Alexander Monakov
1 sibling, 1 reply; 8+ messages in thread
From: Rich Felker @ 2016-09-15 3:27 UTC (permalink / raw)
To: musl
On Wed, Sep 14, 2016 at 11:02:16PM -0400, Felix Janda wrote:
> gdb's "info threads" displays the thread name.
> ---
> Should this function care about interrupted syscalls?
Unless it's specified not to return EINTR I'm fine with it returning
EINTR.
> ---
> include/pthread.h | 1 +
> src/thread/pthread_setname_np.c | 21 +++++++++++++++++++++
> 2 files changed, 22 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..b7f7a4b
> --- /dev/null
> +++ b/src/thread/pthread_setname_np.c
> @@ -0,0 +1,21 @@
> +#include <fcntl.h>
> +#include <string.h>
> +#include <unistd.h>
> +
> +#include "pthread_impl.h"
> +
> +int pthread_setname_np(pthread_t thread, const char *name)
> +{
> + int fd, status = 0;
> + char f[sizeof "/proc/self/task//comm" + 7];
Where does 7 come from? I don't think it's correct. 3*sizeof(int) is
the normal lazy bound we use for %d's.
> + ssize_t len;
> +
> + if ((len = strlen(name)) > 15) return ERANGE;
Storing the result of strlen in a ssize_t is odd. It works because no
object can be larger than SIZE_MAX/2, but it's ugly. Also using
strnlen would be preferable if there's a limit (so as not to read
unboundedly long strings only to reject them).
> +
> + snprintf(f, sizeof f, "/proc/self/task/%d/comm", thread->tid);
> + if ((fd = open(f, O_WRONLY)) < 0) return errno;
> + if (write(fd, name, len) < 0) status = errno;
> +
> + close(fd);
This needs blocking of the cancellation points, I think.
Rich
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH RFC] add pthread_setname_np
2016-09-15 3:27 ` Rich Felker
@ 2016-09-15 3:43 ` Felix Janda
2016-09-15 4:17 ` Rich Felker
0 siblings, 1 reply; 8+ messages in thread
From: Felix Janda @ 2016-09-15 3:43 UTC (permalink / raw)
To: musl
Rich Felker wrote:
Thanks for the review!
> On Wed, Sep 14, 2016 at 11:02:16PM -0400, Felix Janda wrote:
> > gdb's "info threads" displays the thread name.
> > ---
> > Should this function care about interrupted syscalls?
>
> Unless it's specified not to return EINTR I'm fine with it returning
> EINTR.
ok. Is it possible that write() is interrupted with partial data
written (so that it won't return -1)?
> > ---
> > include/pthread.h | 1 +
> > src/thread/pthread_setname_np.c | 21 +++++++++++++++++++++
> > 2 files changed, 22 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..b7f7a4b
> > --- /dev/null
> > +++ b/src/thread/pthread_setname_np.c
> > @@ -0,0 +1,21 @@
> > +#include <fcntl.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +
> > +#include "pthread_impl.h"
> > +
> > +int pthread_setname_np(pthread_t thread, const char *name)
> > +{
> > + int fd, status = 0;
> > + char f[sizeof "/proc/self/task//comm" + 7];
>
> Where does 7 come from? I don't think it's correct. 3*sizeof(int) is
> the normal lazy bound we use for %d's.
man 5 proc
says that the maximum value for a pid is about 4 million. I'm fine with
to changing it to the usual lazy bound, though.
> > + ssize_t len;
> > +
> > + if ((len = strlen(name)) > 15) return ERANGE;
>
> Storing the result of strlen in a ssize_t is odd. It works because no
> object can be larger than SIZE_MAX/2, but it's ugly. Also using
> strnlen would be preferable if there's a limit (so as not to read
> unboundedly long strings only to reject them).
ssize_t is a remnant from reusing len for the return value of write().
Will fix both issues.
> > +
> > + snprintf(f, sizeof f, "/proc/self/task/%d/comm", thread->tid);
> > + if ((fd = open(f, O_WRONLY)) < 0) return errno;
> > + if (write(fd, name, len) < 0) status = errno;
> > +
> > + close(fd);
>
> This needs blocking of the cancellation points, I think.
Will look into it.
Thanks,
Felix
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH RFC] add pthread_setname_np
2016-09-15 3:43 ` Felix Janda
@ 2016-09-15 4:17 ` Rich Felker
2016-09-15 12:00 ` Felix Janda
0 siblings, 1 reply; 8+ messages in thread
From: Rich Felker @ 2016-09-15 4:17 UTC (permalink / raw)
To: musl
On Wed, Sep 14, 2016 at 11:43:51PM -0400, Felix Janda wrote:
> Rich Felker wrote:
>
> Thanks for the review!
>
> > On Wed, Sep 14, 2016 at 11:02:16PM -0400, Felix Janda wrote:
> > > gdb's "info threads" displays the thread name.
> > > ---
> > > Should this function care about interrupted syscalls?
> >
> > Unless it's specified not to return EINTR I'm fine with it returning
> > EINTR.
>
> ok. Is it possible that write() is interrupted with partial data
> written (so that it won't return -1)?
That won't happen with these proc pseudo-files because the write is
required by the kernel to be atomic. If it's broken up into multiple
parts, the kernel only uses the last one.
> > > include/pthread.h | 1 +
> > > src/thread/pthread_setname_np.c | 21 +++++++++++++++++++++
> > > 2 files changed, 22 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..b7f7a4b
> > > --- /dev/null
> > > +++ b/src/thread/pthread_setname_np.c
> > > @@ -0,0 +1,21 @@
> > > +#include <fcntl.h>
> > > +#include <string.h>
> > > +#include <unistd.h>
> > > +
> > > +#include "pthread_impl.h"
> > > +
> > > +int pthread_setname_np(pthread_t thread, const char *name)
> > > +{
> > > + int fd, status = 0;
> > > + char f[sizeof "/proc/self/task//comm" + 7];
> >
> > Where does 7 come from? I don't think it's correct. 3*sizeof(int) is
> > the normal lazy bound we use for %d's.
>
> man 5 proc
>
> says that the maximum value for a pid is about 4 million. I'm fine with
> to changing it to the usual lazy bound, though.
Ah. That may be true for all current versions of Linux, but I don't
think it counts as part of the API/ABI. The ABI limit on pids is 512M
IIRC (because high bits have special meaning in robust/PI futex ABI).
Rich
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH RFC] add pthread_setname_np
2016-09-15 4:17 ` Rich Felker
@ 2016-09-15 12:00 ` Felix Janda
0 siblings, 0 replies; 8+ messages in thread
From: Felix Janda @ 2016-09-15 12:00 UTC (permalink / raw)
To: musl
Rich Felker wrote:
> On Wed, Sep 14, 2016 at 11:43:51PM -0400, Felix Janda wrote:
> > Rich Felker wrote:
> >
> > Thanks for the review!
> >
> > > On Wed, Sep 14, 2016 at 11:02:16PM -0400, Felix Janda wrote:
> > > > gdb's "info threads" displays the thread name.
> > > > ---
> > > > Should this function care about interrupted syscalls?
> > >
> > > Unless it's specified not to return EINTR I'm fine with it returning
> > > EINTR.
> >
> > ok. Is it possible that write() is interrupted with partial data
> > written (so that it won't return -1)?
>
> That won't happen with these proc pseudo-files because the write is
> required by the kernel to be atomic. If it's broken up into multiple
> parts, the kernel only uses the last one.
Thanks for explaining this!
So the current function will notice that it is interrupted, and return
EINTR.
> > > > include/pthread.h | 1 +
> > > > src/thread/pthread_setname_np.c | 21 +++++++++++++++++++++
> > > > 2 files changed, 22 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..b7f7a4b
> > > > --- /dev/null
> > > > +++ b/src/thread/pthread_setname_np.c
> > > > @@ -0,0 +1,21 @@
> > > > +#include <fcntl.h>
> > > > +#include <string.h>
> > > > +#include <unistd.h>
> > > > +
> > > > +#include "pthread_impl.h"
> > > > +
> > > > +int pthread_setname_np(pthread_t thread, const char *name)
> > > > +{
> > > > + int fd, status = 0;
> > > > + char f[sizeof "/proc/self/task//comm" + 7];
> > >
> > > Where does 7 come from? I don't think it's correct. 3*sizeof(int) is
> > > the normal lazy bound we use for %d's.
> >
> > man 5 proc
> >
> > says that the maximum value for a pid is about 4 million. I'm fine with
> > to changing it to the usual lazy bound, though.
>
> Ah. That may be true for all current versions of Linux, but I don't
> think it counts as part of the API/ABI. The ABI limit on pids is 512M
> IIRC (because high bits have special meaning in robust/PI futex ABI).
Ok, better play it safe.
Will post an updated patch later
Felix
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH RFC] add pthread_setname_np
2016-09-15 3:02 [PATCH RFC] add pthread_setname_np Felix Janda
2016-09-15 3:27 ` Rich Felker
@ 2016-09-15 6:32 ` Alexander Monakov
2016-09-15 11:57 ` Felix Janda
1 sibling, 1 reply; 8+ messages in thread
From: Alexander Monakov @ 2016-09-15 6:32 UTC (permalink / raw)
To: musl
Hi,
On Wed, 14 Sep 2016, Felix Janda wrote:
> --- /dev/null
> +++ b/src/thread/pthread_setname_np.c
> @@ -0,0 +1,21 @@
[...]
> + snprintf(f, sizeof f, "/proc/self/task/%d/comm", thread->tid);
> + if ((fd = open(f, O_WRONLY)) < 0) return errno;
> + if (write(fd, name, len) < 0) status = errno;
Is there a reason to do it this way rather than via prctl(PR_SET_NAME, ...)?
If so, it should be mentioned in the commit message. (I think using prctl
would be more appropriate)
Thanks.
Alexander
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH RFC] add pthread_setname_np
2016-09-15 6:32 ` Alexander Monakov
@ 2016-09-15 11:57 ` Felix Janda
2016-09-15 14:33 ` Rich Felker
0 siblings, 1 reply; 8+ messages in thread
From: Felix Janda @ 2016-09-15 11:57 UTC (permalink / raw)
To: musl
Alexander Monakov wrote:
> Hi,
>
> On Wed, 14 Sep 2016, Felix Janda wrote:
> > --- /dev/null
> > +++ b/src/thread/pthread_setname_np.c
> > @@ -0,0 +1,21 @@
> [...]
> > + snprintf(f, sizeof f, "/proc/self/task/%d/comm", thread->tid);
> > + if ((fd = open(f, O_WRONLY)) < 0) return errno;
> > + if (write(fd, name, len) < 0) status = errno;
>
>
> Is there a reason to do it this way rather than via prctl(PR_SET_NAME, ...)?
> If so, it should be mentioned in the commit message. (I think using prctl
> would be more appropriate)
pthread_setname_np() is more general than prctl(PR_SET_NAME, ...): It can
change the name of any thread, not just the calling one.
Felix
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH RFC] add pthread_setname_np
2016-09-15 11:57 ` Felix Janda
@ 2016-09-15 14:33 ` Rich Felker
0 siblings, 0 replies; 8+ messages in thread
From: Rich Felker @ 2016-09-15 14:33 UTC (permalink / raw)
To: musl
On Thu, Sep 15, 2016 at 07:57:03AM -0400, Felix Janda wrote:
> Alexander Monakov wrote:
> > Hi,
> >
> > On Wed, 14 Sep 2016, Felix Janda wrote:
> > > --- /dev/null
> > > +++ b/src/thread/pthread_setname_np.c
> > > @@ -0,0 +1,21 @@
> > [...]
> > > + snprintf(f, sizeof f, "/proc/self/task/%d/comm", thread->tid);
> > > + if ((fd = open(f, O_WRONLY)) < 0) return errno;
> > > + if (write(fd, name, len) < 0) status = errno;
> >
> > Is there a reason to do it this way rather than via prctl(PR_SET_NAME, ...)?
> > If so, it should be mentioned in the commit message. (I think using prctl
> > would be more appropriate)
>
> pthread_setname_np() is more general than prctl(PR_SET_NAME, ...): It can
> change the name of any thread, not just the calling one.
It might be nice to use prctl if thread==pthread_self(), just to avoid
dependency on /proc in this case. But I think that's a minor detail.
This is a non-critical feature anyway.
Rich
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2016-09-15 14:33 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-09-15 3:02 [PATCH RFC] add pthread_setname_np Felix Janda
2016-09-15 3:27 ` Rich Felker
2016-09-15 3:43 ` Felix Janda
2016-09-15 4:17 ` Rich Felker
2016-09-15 12:00 ` Felix Janda
2016-09-15 6:32 ` Alexander Monakov
2016-09-15 11:57 ` Felix Janda
2016-09-15 14:33 ` Rich Felker
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