request for thread safety advice

php.internals

netcat

22 years ago
Hi, internals. Please send me (post here i mean) a few links about 1. thread safety in general 2. thread saftey in php 3. I'm doing wrapper for librep wich is not thread safe (so mailing archives say). Do I need to know something special ? After doing some googling i found thise for #1 http://www.unix.org/version2/whatsnew/threads.html http://www.unix.org/version2/whatsnew/threadsref.html is that a good reading ? any better suggestions for google requests than thise : c thread safety -mail -archive -lists c thread safety tutor ? I couldn't find anything for #2 but it's not less important than #1 :)
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Rasmus Lerdorf

22 years ago
If the library you are wrapping is not threadsafe, one approach is to simply not worry about it and just mark your extension as not being safe to use in a threaded environment. The majority of people use PHP in a non-threaded environment anyway. If you want to be nice to the folks who do use PHP in a threaded environment, you can look into adding a semaphore lock around the calls into the code that is not threadsafe. Such a semaphore lock makes sure that only 1 thread at a time can enter the code. Other threads sit around and wait until it is their turn. -Rasmus On Mon, 20 Oct 2003, netcat wrote:

Uwe Schindler

22 years ago
nice for that would be some macros (somewhere in zend????) which help in the following way (the ext_skel should generate the code, too): a) define a global library identifier (for all blocks that should not run at the same time) zend_create_mutex(identifier) b) use some code like: zend_start_synchronized(identifier) { ... ... } zend_end_synchronized(identifier); (Same construct like zend_try). Without ZTS this macros should be empty... As I am the developer of the NSAPI SAPI (which runs only with ZTS) I would like to have a GD extension where alle PHP_FUNCTIONs exported from there should have such Java-like "synchronized" blocks. Uwe At 00:10 21.10.2003, you wrote:
>If the library you are wrapping is not threadsafe, one approach is to >simply not worry about it and just mark your extension as not being safe >to use in a threaded environment. The majority of people use PHP in a >non-threaded environment anyway. > >If you want to be nice to the folks who do use PHP in a threaded >environment, you can look into adding a semaphore lock around the calls >into the code that is not threadsafe. Such a semaphore lock makes sure >that only 1 thread at a time can enter the code. Other threads sit around >and wait until it is their turn. > >-Rasmus > >On Mon, 20 Oct 2003, netcat wrote: > > > Hi, internals. > > > > Please send me (post here i mean) a few links about > > 1. thread safety in general > > 2. thread saftey in php > > 3. I'm doing wrapper for librep wich is not thread > > safe (so mailing archives say). Do I need to know > > something special ? > > > > > > After doing some googling i found thise for #1 > > http://www.unix.org/version2/whatsnew/threads.html > > http://www.unix.org/version2/whatsnew/threadsref.html > > is that a good reading ? > > > > any better suggestions for google requests than thise : > > c thread safety -mail -archive -lists > > c thread safety tutor > > ? > > > > I couldn't find anything for #2 but it's not less > > important than #1 :) > > > > > > > >-- >PHP Internals - PHP Runtime Development Mailing List >To unsubscribe, visit: http://www.php.net/unsub.php
----- Uwe Schindler thetaphi@php.net - http://www.php.net NSAPI SAPI developer Erlangen, Germany

Andi Gutmans

22 years ago
The question is if this is always enough. Say for example hypothetically that the GD library saves the state of the currently being manipulated graphic, it won't be enough to mutex its calls because there's some saved state in between the calls. I'm not sure there's a general way to deal with it. Sure you could have some general code for a mutex but I don't think that'll solve all of the problems. Andi At 02:06 AM 10/21/2003 +0200, Uwe Schindler wrote:

Rasmus Lerdorf

22 years ago
True, I should have mentioned that the mutex might have to span an entire sequence of calls from open to close or something to that effect. In the specific case of GD, it wouldn't actually be hard to make it threadsafe. Shane did it before to GD1 and it should probably be done again for our bundled version of GD2. -Rasmus On Tue, 21 Oct 2003, Andi Gutmans wrote:

Pierre-Alain Joye

22 years ago
On Mon, 20 Oct 2003 17:35:30 -0700 (PDT) Rasmus Lerdorf <rasmus@lerdorf.com> wrote:
> True, I should have mentioned that the mutex might have to span an > entire sequence of calls from open to close or something to that > effect. > > In the specific case of GD, it wouldn't actually be hard to make it > threadsafe. Shane did it before to GD1 and it should probably be done > > again for our bundled version of GD2.
While working on my new gfx lib, I use these macros especially for FT2 and its cache and for the vectors graphics. I did not deeply test and analyze external libs like png, tiff, and others to see if they are really TS, but the most widely used seem to be TS as there is not global static data. But I'm really not a thread expert :-/ I'm interested in every issues you have got using GD2 (bundled) and how you think to solve them (or how have you already solved them). pierre

netcat

22 years ago
netcat wrote:
> Hi, internals. > > Please send me (post here i mean) a few links about > 1. thread safety in general > 2. thread saftey in php > 3. I'm doing wrapper for librep wich is not thread > safe (so mailing archives say). Do I need to know > something special ? > > > After doing some googling i found thise for #1 > http://www.unix.org/version2/whatsnew/threads.html > http://www.unix.org/version2/whatsnew/threadsref.html > is that a good reading ? > > any better suggestions for google requests than thise : > c thread safety -mail -archive -lists > c thread safety tutor > ? > > I couldn't find anything for #2 but it's not less > important than #1 :) > >
Thanks for all the replies. I will probably have more questions when i'll have the time to continue working on the project.
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