[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20160916150038.GM15995@brightrain.aerifal.cx>
Date: Fri, 16 Sep 2016 11:00:38 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] add pthread_setname_np
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
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
