Previously, one shared memory chunk was allocated under mutex and other
chunks (if required) were allocated using atomic operations. So such
allocation is not guaranteed and the result buffer can be less than
requested.
This commit moves multiple chunks allocation under mutex and guarantees
the result buffer is large enough.
"All problems in computer science can be
solved by another level of indirection"
Butler Lampson
Completion handlers for application response buffers executed after
sending the data to client. Application worker can be stopped right
after send response buffers to router. Worker stop causes removal
of all data structures for the worker.
To prevent shared memory segment unmap, need to count the number of
buffers which uses it. So instead of direct reference to shared
memory, need to reference to intermediate 'handler' structure with
use counter and pointer to shared memory.
This allows to use shared memory to communicate with main process.
This patch changes shared memory segment format and breaks compatibility
with older modules.
Do not reuse shared memory segment with different port until this segment
successfully received and indexed on other side. However, segment can be used
to transfer data via the port it was sent at any time.
nxt_port_mmap_t stored in arrays and it is unsafe to store
pointer to array element.
Shared memory structures and macros moved to separate header
file to be used by GO package.
