Re: Re: PHP Performance in Apache: Multi-Process vs Multi-Threaded

On Dec 16, 2010, at 12:28 AM, jvlad wrote: >>> No. Php if we talk about php with all its extensions is not threadsafe >>> at >>> all. Many of the extensions allocate static data and inherently >>> non-thread-safe. >> >> PHP is, if compiled with ZTS/TSRM, thread-safe. Some libraries used by >> some extensions might not be thread safe, but basically all "usually" >> used ones are thread-safe. While it is a bit complicated as some >> libraries could either be compiled thread-safe or not or some might be >> not thread-safe on specific systems ... but that's not PHP itself ;-) >> >> johannes >> > > Dear Johannes, > > I'm not sure why you repeated what I stated in my post. So I'm repeating it > after you too :) > Yes, php core is developed with threadsafe techniques in mind, some > extensions are safe too, and some extensions which are using 3rd party > libraries are definitely not safe. > > The only thing I'd kindly ask you to pay more attention to is using > "usually" word together with "safe" in one sentence. In my opinion they > should never be used both if we talk about production servers, or at least > servers where crashes are not welcome. > > Just to illustrate the issue with "usually", do you consider openssl, a > widely used php extension, as a "usually threadsafe" extension? > If you do, please take a look at this page > http://www.openssl.org/docs/crypto/threads.html and these words > in > particular: > > OpenSSL can safely be used in multi-threaded applications provided that at > least two callback functions are set, locking_function and threadid_func. > locking_function(int mode, int n, const char *file, int line) is needed to > perform locking on shared data structures. (Note that OpenSSL uses a number > of global data structures that will be implicitly shared whenever multiple > threads use OpenSSL.) Multi-threaded applications will crash at random if it > is not set > > > Do you think any locking function is implemented in openssl php extension? > In PHP a SSL_CTX is per thread and is not shared across other threads so it isn't an issue. We don't need to implement any openssl locking functions. An example of non-thread safe is gettext it relies on the locale which is per process and not per-thread. PHP itself at the core is thread safe. As Johannes said most common modules are too. - Scott