Q47933: Effective Limit of 52 Threads Per Process with DosCreateThread

Article: Q47933
Product(s): See article
Version(s): 5.10
Operating System(s): OS/2
Keyword(s): ENDUSER | docerr OpSys PMWin | mspl13_c
Last Modified: 16-JAN-1990

A single process running under OS/2 Version 1.10 or 1.00 is limited to
creating 52 threads with DosCreateThread.

Attempting to create additional threads results in a return value
from DosCreateThread of 155, which is defined as ERROR_TOO_MANY_TCBS
(Thread Control BlockS) in BSEERR.H.

The "Microsoft OS/2 Programmer's Reference," Volume 3, Page 34,
incorrectly states "DosCreateThread can create up to 255 threads per
process." The Reference also fails to note that DosCreateThread could
return ERROR_TOO_MANY_TCBS.

The only way to work around the current OS/2 1.x limitation with
DosCreateThread is by starting additional processes, with each process
being limited to 52 threads. OS/2 1.10 and 1.00 can support up to 255
threads total for all processes in the entire system.

An increase in the limit will be considered for inclusion in a future
release.

Note that threads that will be calling C run-time library functions
should be created with _beginthread, which performs essential library
initializations that DosCreateThread does not perform. The library
function _beginthread is limited to creating 31 threads in C 5.10, for
a total of 32 threads. The next version of C will support the creation
of substantially more threads with its _beginthread.

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