Re: [ast-developers] Re: Putting openat() emulation into libast?
On 16 August 2012 16:16, Glenn Fowler g...@research.att.com wrote: any locking/critical regions will have to use aso because libast itself does not require -l*thread* What about pthread? Is there (on Linux/Unix) any other viable option today? Lionel ___ ast-developers mailing list ast-developers@research.att.com https://mailman.research.att.com/mailman/listinfo/ast-developers
Re: [ast-developers] Re: Putting openat() emulation into libast?
On Thu, 16 Aug 2012 19:28:47 +0200 Lionel Cons wrote: On 16 August 2012 16:16, Glenn Fowler g...@research.att.com wrote: any locking/critical regions will have to use aso because libast itself does not require -l*thread* What about pthread? Is there (on Linux/Unix) any other viable option today? we want -last to be thread safe without using any thread library ___ ast-developers mailing list ast-developers@research.att.com https://mailman.research.att.com/mailman/listinfo/ast-developers
[ast-developers] Re: Putting openat() emulation into libast?
We tend to build new APIs along with our needs to make
sure that these APIs are actually useful. ASO is like that.
It was written primarily to abstract out the primitives
required to support concurrency in CDT and Vmalloc.
It is, by no means, a complete library for all
traditional atomic operations. The available locking
routine basically implements spin-lock with no nesting.
As time goes on, new primitives will be added.
Mutex will probably be added around when I start
hacking Sfio because of sfmutex().
Phong
From olga.kryzhanov...@gmail.com Thu Aug 16 10:22:01 2012
Subject: Re: Putting openat() emulation into libast?
To: Glenn Fowler g...@research.att.com, Phong Vo k...@research.att.com
Cc: ast-developers@research.att.com, d...@research.att.com,
roland.ma...@nrubsig.org
Phong, how do I use aso to get an exclusive lock/mutex, and release
it? Can a aso lock/mutex be nested?
Olga
On Thu, Aug 16, 2012 at 4:16 PM, Glenn Fowler g...@research.att.com wrote:
any locking/critical regions will have to use aso
because libast itself does not require -l*thread*
On Thu, 16 Aug 2012 16:11:16 +0200 =?KOI8-R?B?z8zYx8Egy9LZ1sHOz9fTy8HR?=
wrote:
Glenn, is the general plan of putting a openat() emulation into libast
acceptable for you? I found that Roland wrote one in 2004 with threads
in mind, and that it only needs polishing and testing. If you agree to
take it I can spend some time this evening on it.
Olga
On Thu, Aug 16, 2012 at 1:20 AM, Glenn Fowler g...@research.att.com
wrote:
On Thu, 16 Aug 2012 01:09:29 +0200 =?KOI8-R?B?z8zYx8Egy9LZ1sHOz9fTy8HR?=
wrote:
Glenn, have you ever considered putting an openat(), fstatat(),
mkfifoat() emulation into libast, if the base operating system does
not have such calls? I have been trying more tests with the at() apis
but I am not happy to trash much of libshell with lots of #ifdef
AT_CWD tests if there is a better option.
AFAIK a lot of the at() calls can be emulated by using
/dev/fd/${dirfd}/${path} or /proc/${pid}/fd/${dirfd}/${path}. I just
do not know, are there cases where /dev/fd or /proc/${pid}/fd are not
available (chroot environments?)?
there are a lot of systems with lame or no /proc
and it will be hard to work around systems with no O_search
but let me think a bit on that
if we didn't have to worry about dir fd's across exec (probably rare
right now)
we might be able to cache emulated open(O_search) paths with dev,ino
keys
on systems that don't support /dev/fd/FD/PATH pr
/proc/PID/fd/FD/PATH
Olga
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[ast-developers] Re: Putting openat() emulation into libast?
Glenn, how to an application obtain a fd just using dev,ino?
The alternative, if no /proc or /dev/fd is available, is to save the
cwd, do a temporary cwd using fchdir(), and restore the old cwd. This
is now glibc did it, with a mutex around the whole sequence to make it
thread safe.
Olga
On Thu, Aug 16, 2012 at 1:20 AM, Glenn Fowler g...@research.att.com wrote:
On Thu, 16 Aug 2012 01:09:29 +0200 =?KOI8-R?B?z8zYx8Egy9LZ1sHOz9fTy8HR?=
wrote:
Glenn, have you ever considered putting an openat(), fstatat(),
mkfifoat() emulation into libast, if the base operating system does
not have such calls? I have been trying more tests with the at() apis
but I am not happy to trash much of libshell with lots of #ifdef
AT_CWD tests if there is a better option.
AFAIK a lot of the at() calls can be emulated by using
/dev/fd/${dirfd}/${path} or /proc/${pid}/fd/${dirfd}/${path}. I just
do not know, are there cases where /dev/fd or /proc/${pid}/fd are not
available (chroot environments?)?
there are a lot of systems with lame or no /proc
and it will be hard to work around systems with no O_search
but let me think a bit on that
if we didn't have to worry about dir fd's across exec (probably rare right
now)
we might be able to cache emulated open(O_search) paths with dev,ino keys
on systems that don't support /dev/fd/FD/PATH pr
/proc/PID/fd/FD/PATH
Olga
--
, __ ,
{ \/`o;-Olga Kryzhanovska -;o`\/ }
.'-/`-/ olga.kryzhanov...@gmail.com \-`\-'.
`'-..-| / http://twitter.com/fleyta \ |-..-'`
/\/\ Solaris/BSD//C/C++ programmer /\/\
`--` `--`
--
, __ ,
{ \/`o;-Olga Kryzhanovska -;o`\/ }
.'-/`-/ olga.kryzhanov...@gmail.com \-`\-'.
`'-..-| / http://twitter.com/fleyta \ |-..-'`
/\/\ Solaris/BSD//C/C++ programmer /\/\
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[ast-developers] Re: Putting openat() emulation into libast?
Glenn, I think the only portable way is to do a open(., O_RDONLY),
and if that fails save the name from getcwd(), and restore that, if
neither /dev/fd or /proc/${pid}/fd/${dirfd} are working. As far as I
know there is no way to open a file using dev,ino, and dev,ino may
not be reliable for all kinds of file systems, such like as fuse
(http://en.wikipedia.org/wiki/Filesystem_in_Userspace).
Olga
On Thu, Aug 16, 2012 at 1:24 AM, ольга крыжановская
olga.kryzhanov...@gmail.com wrote:
Glenn, how to an application obtain a fd just using dev,ino?
The alternative, if no /proc or /dev/fd is available, is to save the
cwd, do a temporary cwd using fchdir(), and restore the old cwd. This
is now glibc did it, with a mutex around the whole sequence to make it
thread safe.
Olga
On Thu, Aug 16, 2012 at 1:20 AM, Glenn Fowler g...@research.att.com wrote:
On Thu, 16 Aug 2012 01:09:29 +0200 =?KOI8-R?B?z8zYx8Egy9LZ1sHOz9fTy8HR?=
wrote:
Glenn, have you ever considered putting an openat(), fstatat(),
mkfifoat() emulation into libast, if the base operating system does
not have such calls? I have been trying more tests with the at() apis
but I am not happy to trash much of libshell with lots of #ifdef
AT_CWD tests if there is a better option.
AFAIK a lot of the at() calls can be emulated by using
/dev/fd/${dirfd}/${path} or /proc/${pid}/fd/${dirfd}/${path}. I just
do not know, are there cases where /dev/fd or /proc/${pid}/fd are not
available (chroot environments?)?
there are a lot of systems with lame or no /proc
and it will be hard to work around systems with no O_search
but let me think a bit on that
if we didn't have to worry about dir fd's across exec (probably rare right
now)
we might be able to cache emulated open(O_search) paths with dev,ino keys
on systems that don't support /dev/fd/FD/PATH pr
/proc/PID/fd/FD/PATH
Olga
--
, __ ,
{ \/`o;-Olga Kryzhanovska -;o`\/ }
.'-/`-/ olga.kryzhanov...@gmail.com \-`\-'.
`'-..-| / http://twitter.com/fleyta \ |-..-'`
/\/\ Solaris/BSD//C/C++ programmer /\/\
`--` `--`
--
, __ ,
{ \/`o;-Olga Kryzhanovska -;o`\/ }
.'-/`-/ olga.kryzhanov...@gmail.com \-`\-'.
`'-..-| / http://twitter.com/fleyta \ |-..-'`
/\/\ Solaris/BSD//C/C++ programmer /\/\
`--` `--`
--
, __ ,
{ \/`o;-Olga Kryzhanovska -;o`\/ }
.'-/`-/ olga.kryzhanov...@gmail.com \-`\-'.
`'-..-| / http://twitter.com/fleyta \ |-..-'`
/\/\ Solaris/BSD//C/C++ programmer /\/\
`--` `--`
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