[help-serveez] Thread safety

[Andreas Rottmann]

Hi!

I'm using threads in my serveez-based application and now wonder about
the thread-safety of svz_log() (since it would be nice to be able to
use it from the additional threads, too). AFAICT, There are the
following issues: 

a) Thread safety of the C stdio functions (FILE *). I'm not really
   sure about this, but I guess they are not really thread-safe when used
   on the same FILE *.
   
b) svz_log uses localtime, which is not thread-safe. However,
   according to the libc info, there is localtime_r, defined by
   POSIX.1c.

c) svz_log accesses svz_config (see a)) and svz_logfile, so they would
   need to be locked.

Solutions would be IMO:

a) Simply lock access to svz_logfile. This can be done quite easily,
   because svz_logfile is static.

b) Use localtime_r, if available.

c) This is a bit hairy. svz_config is *not* static. IMO, It would be
   wise to make it static and use accessor functions. Then it could be
   locked.

I'd be glad to provide a patch that makes svz_log thread-safe (or
mostly so ;-)), but before I want to hear comments on c), since making
svz_config static would result in API breakage.

Regards, Andy
-- 
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