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Added a workaround for a minor scheduling bug + documentation.

This commit is contained in:
profi200 2020-09-08 16:17:07 +02:00
parent 02e9fa9830
commit 6826d5d660
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GPG Key ID: 17B42AE5911139F3
1 changed files with 14 additions and 1 deletions
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15
kernel/source/kernel.c
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@ -167,7 +167,20 @@ bool waitQueueWakeN(ListNode *waitQueue, u32 wakeCount, KRes res, bool reschedul
do
{
TaskCb *task = LIST_ENTRY(listPopHead(waitQueue), TaskCb, node);
/*
* Edge case:
* 2 tasks, 1 single shot event. Task 2 waits first and then task 1.
* When signaled (by an IRQ) only task 1 will ever run instead of
* alternating between both because task 1 always lands on the
* head (as intended) but on wakeup we take N tasks from the head
* to preserve order.
*
* Workaround:
* Take tasks from the tail instead. This will however punish
* the longest waiting tasks unnecessarily.
*/
//TaskCb *task = LIST_ENTRY(listPopHead(waitQueue), TaskCb, node);
TaskCb *task = LIST_ENTRY(listPop(waitQueue), TaskCb, node);
readyBitmap |= 1u<<task->prio;
task->res = res;
listPushTail(&runQueues[task->prio], &task->node);