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[glibc] Deleted branch azanella/y2038-preliminaries
- From: Adhemerval Zanella <azanella at sourceware dot org>
- To: glibc-cvs at sourceware dot org
- Date: 31 Oct 2019 14:12:36 -0000
- Subject: [glibc] Deleted branch azanella/y2038-preliminaries
The branch 'azanella/y2038-preliminaries' was deleted.
It previously pointed to:
8373719... Revise the documentation of simple calendar time.
Diff:
!!! WARNING: THE FOLLOWING COMMITS ARE NO LONGER ACCESSIBLE (LOST):
-------------------------------------------------------------------
8373719... Revise the documentation of simple calendar time.
8860ddf... Make second argument of gettimeofday as 'void *'
ec2eecf... Use clock_gettime to implement gettimeofday.
8390b0f... Use clock_gettime to implement timespec_get.
68dfb40... Consolidate and deprecate ftime
ec97ba2... Change most internal uses of time to __clock_gettime.
bfc9f61... Use clock_gettime to implement time.
6203fd6... Use clock_settime to implement settimeofday.
8fba8f1... Use clock_settime to implement stime; withdraw stime.
16079f4... Change most internal uses of __gettimeofday to __clock_gett
6ab2b36... Linux/Alpha: don't use timeval32 system calls.
commit 8373719be7abcc5bf8618a580982063e1fa0eeac
Author: Zack Weinberg <zackw@panix.com>
Date: Mon Aug 19 10:31:07 2019 -0400
Revise the documentation of simple calendar time.
This is a thorough revision of all the material relating to the
functions time, stime, gettimeofday, settimeofday, clock_gettime,
clock_getres, clock_settime, and difftime, spilling over into the
discussion of time-related data types (which now get their own
section) and touching the adjtime family as well (which deserves its
own thorough revision, but I'd have to do a bunch of research first).
Substantive changes are:
* Document clock_gettime, clock_getres, and clock_settime. (Only
CLOCK_REALTIME and CLOCK_MONOTONIC are documented; the others are
either a bit too Linux-specific, or have more to do with measuring
CPU/processor time. That section _also_ deserves its own thorough
revision but again I'd have to do a bunch of research first.)
* Present gettimeofday, settimeofday, and struct timeval as obsolete
relative to clock_*.
* Remove the documentation of struct timezone. Matching POSIX,
say that the type of the second argument to gettimeofday and
settimeofday is [const] void *.
* Clarify ISO C and POSIX's requirements on time_t. Clarify the
circumstances under which difftime is equivalent to simple
subtraction.
* Consolidate documentation of most of the time-related data types
into a new section "Time Types," right after "Time Basics." (The
exceptions are struct tm, which stays in "Broken-down Time," and
struct times, which stays in "Processor And CPU Time."
* The "Elapsed Time" section is now called "Calculating Elapsed Time"
and includes only difftime and the discussion of how to compute
timeval differences by hand.
* Fold the "Simple Calendar Time," "High Resolution Calendar," and
"High Accuracy Clock" sections together into two new sections titled
"Getting the Time" and "Setting and Adjusting the Time."
commit 8860ddfdac37caa8a781c93c0530b550e16705c7
Author: Zack Weinberg <zackw@panix.com>
Date: Mon Aug 19 13:51:25 2019 -0400
Make second argument of gettimeofday as 'void *'
Also make the public prototype of gettimeofday declare its second
argument with type "void *" unconditionally, consistent with POSIX.
It is also consistent with POSIX.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu.
Co-authored-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
commit ec2eecfcc064d6ea55142836f3ff9bb811de77ff
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Thu Oct 24 19:19:33 2019 +0000
Use clock_gettime to implement gettimeofday.
Consolidate generic gettimeofday implementation to use clock_gettime.
Linux ports that still provide gettimeofday through vDSO are not
changed.
Remove sysdeps/unix/clock_gettime.c, which implemented clock_gettime
using gettimeofday; new OS ports must provide a real implementation of
clock_gettime.
Rename sysdeps/mach/gettimeofday.c to sysdeps/mach/clock_gettime.c and
convert into an implementation of clock_gettime. It only supports
CLOCK_REALTIME; Mach does not appear to have any support for monotonic
clocks. It uses __host_get_time, which provides at best microsecond
resolution. Hurd is currently using sysdeps/posix/clock_getres.c for
clock_getres; its output for CLOCK_REALTIME is based on
sysconf (_SC_CLK_TCK), and I do not know whether that gives the
correct result.
Unlike settimeofday, there are no known uses of gettimeofday's
vestigial "get time zone" feature that are not bugs. (The per-process
timezone support in localtime and friends is unrelated, and the
programs that set the kernel's offset between the hardware clock and
UTC do not need to read it back.) Therefore, this feature is dummied
out. Henceforth, if gettimeofday's "struct timezone" argument is not
NULL, it will write zeroes to both fields. Any program that is
actually looking at this data will thus think it is running in UTC,
which is probably more correct than whatever it was doing before.
[__]gettimeofday no longer has any internal callers, so we can now
remove its internal prototype and PLT bypass aliases. The
__gettimeofday@GLIBC_2.0 export remains, in case it is used by any
third-party code.
It also allows to simplify the arch-specific implementation on x86 and
powerpc to remove the hack to disable the internal route to non iFUNC
variant for internal symbol.
This patch also fixes a missing optimization on aarch64, powerpc, and
x86 where the code used on static build do not use the vDSO.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu.
Co-authored-by: Zack Weinberg <zackw@panix.com>
commit 8390b0ff848ee65c47fdd49cf818a746defead99
Author: Zack Weinberg <zackw@panix.com>
Date: Thu Aug 22 17:10:35 2019 -0400
Use clock_gettime to implement timespec_get.
timespec_get is the same function as clock_gettime, with an obnoxious
coating of NIH painted on it by the ISO C committee. In addition to
the rename, it takes its arguments in a different order, it returns 0
on *failure* or a positive number on *success*, and it requires that
all of its TIME_* constants be positive. This last means we cannot
directly reuse the existing CLOCK_* constants for it, because
those have been allocated starting with CLOCK_REALTIME = 0 on all
existing platforms.
This patch simply promotes the sysdeps/posix implementation to
universal, and removes the Linux-specific implementation, whose
apparent reason for existing was to cut out one function call's worth
of overhead.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu.
commit 68dfb406a9d4a244358e7e6bd6d752f19f8a703a
Author: Zack Weinberg <zackw@panix.com>
Date: Wed Sep 4 16:51:23 2019 +0000
Consolidate and deprecate ftime
ftime is an obsolete variation on gettimeofday, offering only
millisecond time resolution; it was probably a system call in ooold
versions of BSD Unix. For historic reasons, we had three
implementations of it. These are all consolidated into time/ftime.c,
and then the function is deprecated.
For some reason, the implementation of ftime in terms of gettimeofday
was rounding rather than truncating microseconds to milliseconds. In
all the other places where we use a higher-resolution time function to
implement a lower-resolution one, we truncate. ftime is changed to
match, just for tidiness' sake.
Like gettimeofday, ftime tries to report the time zone, and using that
information is always a bug. This patch dummies out the reported
timezone information; the timezone and dstflag fields of the
returned "struct timeb" will always be zero.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, and powerpc-linux-gnu.
Co-authored-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
commit ec97ba21a650bab7cd22c7b0da351974ebdc5f1b
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Thu Oct 24 21:01:40 2019 +0000
Change most internal uses of time to __clock_gettime.
As for gettimeofday, time will be implemented based on clock_gettime
on all platforms and internal code should use clock_gettime
directly. In addition to removing a layer of indirection, this will
allow us to remove the PLT-bypass gunk for gettimeofday.
The changed code always assumes __clock_gettime (CLOCK_REALTIME)
or __clock_gettime (CLOCK_REALTIME_COURSE) (for Linux case) cannot
fail, using the same rationale for gettimeofday change. And internal
helper was added (time_now).
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, and powerpc-linux-gnu.
commit bfc9f6179a0fdb070428010b0c5f022cca4a8c9d
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Thu Oct 24 17:52:30 2019 +0000
Use clock_gettime to implement time.
Change the default implementation of time to call clock_gettime,
to align with new Linux ports that are expected to only implement
__NR_clock_gettime. Arch-specific implementation that either call
the time vDSO or route to gettimeofday vDSO are not removed.
Also for Linux, CLOCK_REALTIME_COARSE is used instead of generic
CLOCK_REALTIME clockid. This takes less CPU time and its behavior
better matches what the current glibc does.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu.
Co-authored-by: Zack Weinberg <zackw@panix.com>
commit 6203fd6ed5c8ed242cf7d13af7722f056207eefb
Author: Zack Weinberg <zackw@panix.com>
Date: Wed Aug 28 08:25:49 2019 -0400
Use clock_settime to implement settimeofday.
Unconditionally, on all ports, use clock_settime to implement
settimeofday. Remove sysdeps/unix/clock_settime.c, which implemented
clock_settime by calling settimeofday; new OS ports must henceforth
provide a real implementation of clock_settime.
Hurd had a real implementation of settimeofday but not of
clock_settime; this patch converts it into an implementation of
clock_settime. It only supports CLOCK_REALTIME and microsecond
resolution; Hurd/Mach does not appear to have any support for
finer-resolution clocks.
The vestigial "set time zone" feature of settimeofday complicates the
generic settimeofday implementation a little. The only remaining uses
of this feature that aren't just bugs, are using it to inform the
Linux kernel of the offset between the hardware clock and UTC, on
systems where the hardware clock doesn't run in UTC (usually because
of dual-booting with Windows). There currently isn't any other way to
do this. However, the callers that do this call settimeofday with
_only_ the timezone argument non-NULL. Therefore, glibc's new
behavior is: callers of settimeofday must supply one and only one of
the two arguments. If both arguments are non-NULL, or both arguments
are NULL, the call fails and sets errno to EINVAL.
When only the timeval argument is supplied, settimeofday calls
__clock_settime(CLOCK_REALTIME), same as stime.
When only the timezone argument is supplied, settimeofday calls a new
internal function called __settimezone. On Linux, only, this function
will pass the timezone structure to the settimeofday system call. On
all other operating systems, and on Linux architectures that don't
define __NR_settimeofday, __settimezone is a stub that always sets
errno to ENOSYS and returns -1.
The settimeoday syscall is enabled on Linux by the flag
COMPAT_32BIT_TIME, which is an option to either 32-bits ABIs or COMPAT
builds (defined usually by 64-bit kernels that want to support 32-bit
ABIs, such as x86). The idea to future 64-bit time_t only ABIs
is to not provide settimeofday syscall.
The same semantics are implemented for Linux/Alpha's GLIBC_2.0 compat
symbol for settimeofday.
There are no longer any internal callers of __settimeofday, so the
internal prototype is removed.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
commit 8fba8f190900f725492e32376c4f70497a80dc6b
Author: Zack Weinberg <zackw@panix.com>
Date: Fri Aug 16 15:03:16 2019 -0400
Use clock_settime to implement stime; withdraw stime.
Unconditionally, on all ports, use clock_settime to implement stime,
not settimeofday or a direct syscall. Then convert stime into a
compatibility symbol and remove its prototype from time.h.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
commit 16079f436d4d29c74dfefd1862e52b02f3823918
Author: Zack Weinberg <zackw@panix.com>
Date: Fri Aug 16 20:38:22 2019 -0400
Change most internal uses of __gettimeofday to __clock_gettime.
Since gettimeofday will shortly be implemented in terms of
clock_gettime on all platforms, internal code should use clock_gettime
directly; in addition to removing a layer of indirection, this will
allow us to remove the PLT-bypass gunk for gettimeofday. (We can't
quite do that yet, but it'll be coming later in this patch series.)
In many cases, the changed code does fewer conversions.
The changed code always assumes __clock_gettime (CLOCK_REALTIME)
cannot fail. Most of the call sites were assuming gettimeofday could
not fail, but a few places were checking for errors. POSIX says
clock_gettime can only fail if the clock constant is invalid or
unsupported, and CLOCK_REALTIME is the one and only clock constant
that's required to be supported. For consistency I grepped the entire
source tree for any other places that checked for errors from
__clock_gettime (CLOCK_REALTIME), found one, and changed it too.
(For the record, POSIX also says gettimeofday can never fail.)
(It would be nice if we could declare that GNU systems will always
support CLOCK_MONOTONIC as well as CLOCK_REALTIME; there are several
places where we are using CLOCK_REALTIME where _MONOTONIC would be
more appropriate, and/or trying to use _MONOTONIC and then falling
back to _REALTIME. But the Hurd doesn't support CLOCK_MONOTONIC yet,
and it looks like adding it would involve substantial changes to
gnumach's internals and API. Oh well.)
A few Hurd-specific files were changed to use __host_get_time instead
of __clock_gettime, as this seemed tidier. We also assume this cannot
fail. Skimming the code in gnumach leads me to believe the only way
it could fail is if __mach_host_self also failed, and our
Hurd-specific code consistently assumes that can't happen, so I'm
going with that.
With the exception of support/support_test_main.c, test cases are not
modified, mainly because I didn't want to have to figure out which
test cases were testing gettimeofday specifically.
The definition of GETTIME in sysdeps/generic/memusage.h had a typo and
was not reading tv_sec at all. I fixed this. It appears nobody has been
generating malloc traces on a machine that doesn't have a superseding
definition.
There are a whole bunch of places where the code could be simplified
by factoring out timespec subtraction and/or comparison logic, but I
want to keep this patch as mechanical as possible.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
commit 6ab2b361543488a0086345e28b3e199cae84a79f
Author: Zack Weinberg <zackw@panix.com>
Date: Mon Aug 19 14:18:08 2019 -0400
Linux/Alpha: don't use timeval32 system calls.
Linux/Alpha has two versions of several system call wrappers that take
or return data of type "struct timeval" (possibly nested inside a
larger structure). The GLIBC_2.0 version is a compat symbol that
calls __NR_osf_foo or __NR_old_foo and uses a struct timeval with a
32-bit tv_sec field. The GLIBC_2.1 version is used for current code,
calls __NR_foo, and uses a struct timeval with a 64-bit tv_sec field.
This patch changes all of the compat symbols of this type to be
wrappers around their GLIBC_2.1 counterparts; the compatibility system
calls will no longer be used. It serves as a proposal for part of how
we do the transition to 64-bit time_t on systems that currently use
32-bit time_t:
* The patched glibc will NOT use system calls that involve 32-bit
time_t to implement its compatibility symbols. This will make both
our lives and the kernel maintainers' lives easier. The primary
argument I've seen against it is that the kernel could warn about
uses of the old system calls, helping people find old binaries that
need to be recompiled. I think there are several other ways we
could accomplish this, e.g. scripts to scan the filesystem for
binaries with references to the old symbol versions, or issuing
diagnostics ourselves.
* The compat symbols do NOT report failure after the Y2038 deadline.
An earlier revision of this patch had them return -1 and set errno
to EOVERFLOW, but Adhemerval pointed out that many of them have
already performed side effects at the point where we discover the
overflow, so that would break more than it fixes. Also, we don't
want people to be _checking_ for EOVERFLOW from these functions; we
want them to recompile with 64-bit time_t. So it's not actually
useful for them to report failure to the calling code.
* What they do do, when they encounter overflow, is saturate the
overflowed "struct timeval"(s): tv_sec is set to INT32_MAX and
tv_nsec is set to 999999. That means time stops advancing for
programs with 32-bit time_t when they reach the deadline. That's
obviously going to break stuff, but I think wrapping around is
probably going to break _more_ stuff. I'd be interested to hear
arguments against, if anyone has one.
The new header file tv32-compat.h is currently Alpha-specific but I
mean for it to be reused to aid in writing wrappers for all affected
architectures. I only put it in sysdeps/unix/sysv/linux/alpha for now
because I haven't checked whether the various "foo32" structures it
defines agree with the ABI for ports other than Linux/Alpha.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>