Re: Semantics of STL containers (std::map) in a multithreaded scenario

"=?iso-8859-1?q?Kirit_S=E6lensminde?=" <>
14 Jun 2006 06:27:09 -0700
Dilip wrote:

Thomas J. Gritzan wrote:

Dilip schrieb:
You should not write to a variable in one thread while reading the same
variable in other threads. Its not just about invalidating iterators.

I just looked at the docs for std::map and it looks like for
insertion/removal no iterators are invalidated. So atleast in this
particular case, aren't I safe?

For my company's framework (FOST.3) we've been through this too. What
we did was to define a synchronisation object that allowed a limited
number of read locks or a single write lock. You can have a number of
readers, but only a single write thread at a time accessing the data

If you're writing about as often as you're reading this may not be the
best way. It really depends also on the larger context. Re-architecting
may be an option to sidestep the issue altogether, or using a different
map implementation. Some CPUs offer the possibility of lockless
structures, but they're very hard to implement properly.

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