Hello,

  Is it possible to implement portable disable; and enable;
  procedures? I just know that under dos32v2 you can use disable and
  enable;. Under win32 you can use critical sections for that. And
  seems to be that it is possible to emulate disable; and enable; using
  critical sections. I just wonder if the same is possible under
  linux, os/2 or any other system? Or maybe some unit that provides
  such services already exists?

Best regards,
Aleksey

Hello,

Enable / Disable and critical sections are completely different things...... the first is used for turning off (virtual) interrupts, the other one for thread synchronization.

The key to critical sections is that while they're 'owned' by one thread, another one can't claim ownership for the same critical section object so that the 'owning one' can't get interrupted by others which try to get ownership themselves when doing some mutually exclusive stuff (e.g. writing data to a file). It doesn't prevent other threads from running which don't want to get ownership of the critical section (e.g. don't want to write to the same file).

In a single threaded program critical sections are not worth the writing. Mutexes are similar to critical section objects but with a scope of processes.

Semaphore's are quite similar with the exception that they allow ownership of a specified amount of threads at the same time, e.g. for accessing a limited resource by several threads at the same time.

P.S.: Most likely DPMI servers virtualize the cli and sti instructions too; so the interrupts aren't really disabled in DPMI - PM at all - only the handlers installed by the app doing this are not called. At least in all PM environments like Win9x DOS box it is very unlikely that your application can modify real hardware interrupt state. I recommend the DPMI spec of your choice for further reading about this. This applies to any other PM OS as well btw, you may use enable() and disable() there too - not only go32v2....

Regards,
Thomas

Subject: [fpc-devel]portable disable; and enable;

Hello,

By using disable; and enable; I have not meant to bypass interrupts. Just to make some parts of code uninterruptible by other thread of the same application (under DOS interrupt procedures can be also though as threads). Hm.. Is is possible to create such portable unit that makes parts of code uninterruptible? (yeps, seems to be that semaphores are better examples for disable; and enable; under win32 - there's just a need in one global semaphore).

  I can't suggest any API really... But maybe simple lock; and unlock;
  names are nice? :) Their meaning is so simple I really can't suggest
  anything else...

Best regards,
Aleksey