Re: [boost] [ASIO] Having a hard time after upgrading my boost

[Marat Abrarov]

> My code is heavily multi-threaded. This problem doesn't show up in
> single threaded environment at all. My OS is SUSE 11 and g++-4.3.3 as the
> compiler. I may have to post some code eventually but on the top off your
> head - do you have any pointers for me?

Note that free functions like asio::async_read/aync_read_untill
(async_write/async_write_until, etc) are composed operations so "... The
program must ensure that the stream performs no other read operations (such
as async_read, async_read_until, the stream's async_read_some function, or
any other composed operations that perform reads) until this operation
completes"
(http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/reference/async_re
ad_until.html).

Also note that most of Asio classes (sockets, timers, etc.) are not thread
safe. So in multi-threaded program you have to use some kind of
synchronization if there is no implicit strand
(http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/overview/core/stra
nds.html). The simplest kind of synchronization is asio::io_service::strand.
If you use something else (for example, mutex) then notice intermediate
handlers created by composed operations
(http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/overview/core/stra
nds.html, asio_handler_invoke) and use your synchronization in a right way
(for mutex see
https://github.com/boostcon/2011_presentations/raw/master/mon/thinking_async
hronously.pdf, struct mutex_wrapper at page 95-97).

There is a feature named "Handler Tracking"
(http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/overview/core/hand
ler_tracking.html) that can help you to investigated the order of handler
invocation.

Regards,
Marat Abrarov.



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[Gaetano Mendola]

On 20/05/2013 15.42, Marat Abrarov wrote:
> Also note that most of Asio classes (sockets, timers, etc.) are not thread
> safe. So in multi-threaded program you have to use some kind of
> synchronization if there is no implicit strand
> (http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/overview/core/stra
> nds.html).

The fact that sockets are not thread safe and the usage of strand is
something no related each other.
The fact that ip::tcp::socket are not thread safe imply that you can
not use the same instance from multiple threads (two concurrent
async operation calls for example).
Some time you can not have concurrent handlers calls, so if you have
a pool of threads calling the io_service::run() you have to use
io_service::strand to serialize handler execution.

Regards
Gaetano Mendola