Re: semaphore understanding: sys_semtimedop()
From: Manfred Spraul
Date: Sun May 22 2005 - 01:52:14 EST
randy_dunlap wrote:
On Mon, 16 May 2005 22:17:04 +0200 Patrick Plattes wrote:
| The variable decrease will never be used again in this
| function, so why this intricate code? Isn't this much easier and works
| also:
|
| for (sop = sops; sop < sops + nsops; sop++) {
| if (sop->sem_num >= max)
| max = sop->sem_num;
| if (sop->sem_flg & SEM_UNDO)
| undos++;
| if (sop->sem_op != 0)
| alter = 1;
| }
|
| Maybe i'm totally wrong, so please correct me and don't shoot me up,
| 'cause i'm not a os developer.
Looks like a reasonable and correct optimization to me.
It looks correct:
decrease was added during 2.1 development: it's not in 2.0.40, it's in
2.2.26: I think the idea was that operations with decrease can cause
other threads to block, therefore a different wakeup strategy was used.
The wakeup implementation was rewritten, but the loop remained unchanged.
I'll write a patch, thanks Patrick.
--
Manfred
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