[asio-users] Composed operations not always atomic with strands

[Bjorn R. <br...@ma...>]

I am using async_write() together with a strand in a multi-threaded
program in the same way as in the HTTP server 3 example.

Under heavy load the async_write() operation ceases to be atomic (i.e.
data send by one operation may be interleaved by data from another.)

I have created the attached test case to illustrate the problem. Here
I have two threads sending blocks of data on the same socket. The
receiver is single-threaded, but I have added a sleep() to simulate
slow processing.

When the TCP buffer on the receiver side is full, the sender will only
send part of the data. While the rest will be sent eventually, the
problem is that data submitted by the other thread may be sent
inbetween, so the data is received in the wrong order. The receiver
will assert if this is the case.

Before I create a ticket for this, can anybody find any errors in my
attached examples?