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<hr><p align="left"><small> 在ev_send（）中，说This system call sends events to a task.If the target <br>
task is not waiting for events,the newly sent events are simply made pending. <br>
这里pending 是什么意思？？ev_send()调用会不会等待？？还是立即返回？？ <br>
<br>
发信人: nonsun (无晴), 信区: Embedded <br>
标 题: Re: 请问pending？？？？？？？？？？？？ <br>
发信站: BBS 水木清华站 (Wed Nov 1 23:59:16 2000) <br>
<br>
这个pending是指event的pending，而不是任务的。 <br>
在ev_send()函数里实际上是没有有关阻塞的参数的 <br>
（如超时时间，要注意在实时领域里，绝对不能有 <br>
什么系统调用所耗时间是不可预知的，所以如果一个 <br>
系统调用是可能阻塞的话，它一定是可以指定超时 <br>
设置的）。 <br>
<br>
另外，在ev_receive()函数的解释中其实讲得很清楚 <br>
这个“pending”是什么意思，看看《pSOSystem <br>
Reference Manual》中的《pSOSystem System Calls》 <br>
吧： <br>
<br>
ev_receive <br>
Enables a task to wait for an event condition. <br>
<br>
<br>
Notes <br>
1. Events are not accumulated. No matter how many <br>
identical events are sent to the calling task before <br>
it calls ev_receive() for receiving the event, the <br>
result is the same as if one event were pending. <br>
<br>
2. The ev_receive() call captures only the events <br>
that the caller selects. It captures each selected <br>
event once. If a pending event does not match a <br>
selected event, the pending event remains pending. <br>
Also, if a pending event was sent after an earlier <br>
event was used to match a selected event, the pending <br>
event remains pending. Consider the following example <br>
sequence: <br>
<br>
a. Task P has pending events 1 and 2. <br>
b. With EV_ALL set, P calls ev_receive() for <br>
events 1, 3, and 8. Pending event 1 is cleared. <br>
c. Task A sends events 1 and 8 to P. <br>
d. Event 1 is made pending. Event 8 is used to <br>
match the wanted event. <br>
e. Task B sends events 2, 3, and 5 to P. Event 2 <br>
has no effect because event 2 is already pending. <br>
Event 5 is unwanted and made pending. Event 3 is <br>
used to match a wanted event. The event condition <br>
is met, so P becomes ready to run. <br>
f. Events 1, 2, and 5 are left pending. <br>
g. Events 1, 3, and 8 are returned in events_r. <br>
<br>
<br>
【 在 doot (ltt) 的大作中提到: 】 <br>
: 不会 <br>
<br>
<br>
-- <br>
<br>
我歌月徘徊，我舞影零乱 <br>
<br>
醒时同交欢，醉后各分散 <br>
<br>
<br>
※ 来源:·BBS 水木清华站 smth.org·[FROM: 202.204.7.235] <br>
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