Messages in this thread | | | Date | Fri, 21 Oct 2005 09:03:18 -0400 (EDT) | From | Steven Rostedt <> | Subject | Re: question about code from the linux kernel development ( se ) book |
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Oh God, please indent code examples, and if your email client strips white space, change your email client.
On Fri, 21 Oct 2005, Yitzchak Eidus wrote:
> first i am very sorry if it isnt the place to ask questions like this > but i didnt know where else to ask ( i tryed irc channels and i was > send from there to this list ) > anyway: > does this following code look buggy? :
[ Indention added ]
> DECLARE_WAITQUEUE ( wait , current ); > add_wait_queue ( q , &wait ); > while ( !condition ) { > set_current_stat ( TASK_INTERRUPTABLE ); i > if ( signal_pending ( current ) ) > /* handle signal */
I assume that the signal_pending is the if result and not the schedule. Since there was no indentation I couldn't tell.
> schedule ( ); /* Moved brace down added */ } > set_current_state ( TASK_RUNNING ); > remove_wait_queue ( q , &wait );
Before I go to your questions, I'll first answer that this _is_ buggy code. If the condition is checked and you are woken up between the while (!condition) and the set_current_state, then you will end up sleeping forever or until someone sends you a signal.
> first:doesnt in the way from checking the !condition to > set_current_state the condition can be changed no?
Yes, and then put it again after schedule.
> > second:why not putting the schedule ( ); right after the > set_current_state ( ) , what the point in checking the if ( > signal_pending ( ) first, if the proccess doesnt started to sleep yet?
Yes, I would put the signal_pending check after the schedule (as most of the kernel does this).
> third: in the cleaning in the way from putting the set_current_state ( > TASK_RUNNING ) into remove_wait_queue , cant the queue wait list ( q ) > wake up again the wait procsess?
Yeah, so? There's no harm in that, except for an extra cpu cycles that are done to wake it up. That, I wouldn't change.
> ( thnks for the help , please if it can be done answer quickly i am > tanker in the idf and need to come back to the army soon , ( no > internet there... ) )
BTW, this is not an IRC, we use normal capitalization and normal spelling (when we know how to spell a word ;-). So the next time you send to the list, send it as if you were writing a serious letter, or you may just be ignored. (as you might have been if I didn't respond).
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