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Date: Wed, 14 Sep 2016 23:43:51 -0400
From: Felix Janda <felix.janda@...teo.de>
To: musl@...ts.openwall.com
Subject: Re: [PATCH RFC] add pthread_setname_np
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
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