From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/6001 Path: news.gmane.org!not-for-mail From: Jens Gustedt Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH 2/8] additions to src/time Date: Sun, 31 Aug 2014 09:15:53 +0200 Message-ID: <1409469353.4476.269.camel@eris.loria.fr> References: <20140831001324.GL12888@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-YPjZbTMO3R5bin6RwSDh" X-Trace: ger.gmane.org 1409469361 23136 80.91.229.3 (31 Aug 2014 07:16:01 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 31 Aug 2014 07:16:01 +0000 (UTC) To: musl@lists.openwall.com Original-X-From: musl-return-6008-gllmg-musl=m.gmane.org@lists.openwall.com Sun Aug 31 09:15:56 2014 Return-path: Envelope-to: gllmg-musl@plane.gmane.org Original-Received: from 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Cj15cu23XZI4/826Px/xqB37z547sPH374oOvnKTsOb+1zuCoImZARM8ZiLlKkXcWOcoFRJ+Do/CwFO4e2DEe+9Ti+ZXA8ny/cU+X4bMKRZxZIVEiqXI6/+NKuUzPHb7z40ovnX3zx+Ctuq38HyuqWG7Tu+A0AAAAASUVORK5CYII= X-Mailer: Evolution 3.4.4-3 Xref: news.gmane.org gmane.linux.lib.musl.general:6001 Archived-At: --=-YPjZbTMO3R5bin6RwSDh Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Am Samstag, den 30.08.2014, 20:13 -0400 schrieb Rich Felker: > On Sat, Aug 30, 2014 at 08:46:35PM +0200, Jens Gustedt wrote: > > This adds two functions, thrd_sleep and timespec_get. Both have easy > > functional equivalences in POSIX, but these have subtle differences in > > the handling of errors. > >=20 > > thrd_sleep forces concrete numerical values as error return > >=20 > > timespec_get has a call interface that is incompatible with POSIX becau= se > > it has a bogus coding for its clock constants, and also this clock > > constants must be returned in case of success. For the moment we only > > implement one single clock, TIME_UTC, and map this to > > CLOCK_REALTIME. This is the clock that we later need to measure time fo= r > > the timedlock and timedwait. > >=20 > > Also, other than for clock_gettime, C doesn't specify touching errno fo= r > > timespec_get. Because CLOCK_REALTIME can be obtained very efficiently > > through VDSO and messing with errno is clearly the wrong step to go, we > > try to avoid this. > > --- > > src/time/thrd_sleep.c | 26 ++++++++++++++++++++++++++ > > src/time/timespec_get.c | 31 +++++++++++++++++++++++++++++++ > > 2 files changed, 57 insertions(+) > > create mode 100644 src/time/thrd_sleep.c > > create mode 100644 src/time/timespec_get.c > >=20 > > diff --git a/src/time/thrd_sleep.c b/src/time/thrd_sleep.c > > new file mode 100644 > > index 0000000..3dbfe47 > > --- /dev/null > > +++ b/src/time/thrd_sleep.c > > @@ -0,0 +1,26 @@ > > +#include > > +#include > > +#include "syscall.h" > > +#include "libc.h" > > +#include "threads.h" > > + > > +/* Roughly __syscall already returns the right thing: 0 if all went > > + well or a negative error indication, otherwise. */ > > +int thrd_sleep(const struct timespec *req, struct timespec *rem) > > +{ > > + int ret =3D __syscall(SYS_nanosleep, req, rem); > > + switch (ret) { > > + case 0: > > + return 0; > > + /* error described by POSIX: */ > > + /* EINTR The nanosleep() function was interrupted by a signal. */ > > + /* The C11 wording is: */ > > + /* -1 if it has been interrupted by a signal */ >=20 > Purely coding style, but for musl we generally do multi-line comments > in this form: >=20 > /* line 1 > * line 2 > * line 3 */ I don't remeber having seen that in the coding style recommendations :) I'll fix those that I notice, and keep that in mind for future use. > Using // would be a second-choice alternative. I don't like the > right-alignment of */ with spaces because it will look like a mess to > someone reading it with a non-fixed-width font. >=20 > > diff --git a/src/time/timespec_get.c b/src/time/timespec_get.c > > new file mode 100644 > > index 0000000..20080a0 > > --- /dev/null > > +++ b/src/time/timespec_get.c > > @@ -0,0 +1,31 @@ > > +#include > > +#include "syscall.h" > > +#include "atomic.h" > > + > > +static int syscall_clock_gettime(clockid_t clk, struct timespec *ts) > > +{ > > + return __syscall(SYS_clock_gettime, clk, ts); > > +} > > + > > +void *__vdsosym(const char *, const char *); > > + > > +/* There is no other implemented value than TIME_UTC, all other values > > + are considered erroneous. */ > > +int timespec_get(struct timespec * ts, int base) > > +{ > > + if (base !=3D TIME_UTC) return 0; > > + int ret; > > +#ifdef VDSO_CGT_SYM > > + static int (*cgt)(clockid_t, struct timespec *); > > + if (!cgt) { > > + void *f =3D __vdsosym(VDSO_CGT_VER, VDSO_CGT_SYM); > > + if (!f) f =3D (void *)syscall_clock_gettime; > > + a_cas_p(&cgt, 0, f); > > + } > > + /* The vdso variants never fail, and thus never set errno. */ > > + ret =3D cgt(CLOCK_REALTIME, ts); > > +#else > > + ret =3D syscall_clock_gettime(CLOCK_REALTIME, ts); > > +#endif > > + return ret < 0 ? 0 : base; >=20 > I'd rather not duplicate this code but just call __clock_gettime. ok > Unlike __clock_gettime, your duplicate code does not handle > pre-clock_gettime kernels and will return an error on them. yeah, somehow I missed the gettimeofday syscall. Would it be acceptable by any chance to have a common core for these two functions that doesn't set errno? It would perhaps be appropriate to use such a function in other places of musl, too. Jens --=20 :: INRIA Nancy Grand Est ::: AlGorille ::: ICube/ICPS ::: :: ::::::::::::::: office Strasbourg : +33 368854536 :: :: :::::::::::::::::::::: gsm France : +33 651400183 :: :: ::::::::::::::: gsm international : +49 15737185122 :: :: http://icube-icps.unistra.fr/index.php/Jens_Gustedt :: --=-YPjZbTMO3R5bin6RwSDh Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEABECAAYFAlQCy6kACgkQD9PoadrVN+JplwCcDMSTau5V3Wugrk35TTs0sKJU 7AUAoJGz/meFmowWavZwKPjIv9zAgZVI =RuZm -----END PGP SIGNATURE----- --=-YPjZbTMO3R5bin6RwSDh--