how can i let two process open a resource manager ?

QNX DEVELOPERS General Programming
1

i create a resource manager with thread pool.

but i found a problem with this resource manager X

when processA open X, and excute i/o operation, such as my_write(…)

when processA is blocked by my_write(), processB can’t open X until my_write(…) returns.

so i rewrite my_write() as following

my_read/my_write...(...) { iofunc_attr_unlock(ocb->attr); <--new added .... do_a_cost_much_time_task(); .... iofunc_attr_lock(ocb->attr); <--new added }

now processB can open X when processA is blocked.

why it can works? where ocb->attr is locked?

second question： i tried to use sopen() to let two process to share X, but it seems do not work, processB still blocked. why?

2

The resource manager code that calls your write routine locks the ocb before entering.

3

thank, … but where can i find the resource manager code that calls write routine? in “trunk/lib/c/iofunc”?

i am lookinf for the loop part of a resource manager.

4

If you want to look at it, you would have to download the resource manager source code.

I’ve spent 8+ years happily writing resource managers without ever looking at this code.

How to write a resource manager is one of the best documented parts of QNX. There’s even a third party book by Robert Krten that goes over it in depth.

amazon.com/Getting-Started-N … 497&sr=8-1