Re: [PATCH RFC] add pthread_setname_np

[Felix Janda <felix.janda@posteo.de>]

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