[En-Nut-Discussion] Fingerprints found at crime site....

[Jesper Hansen]

Thread Lurker says:

Fantastic detective work, Michael !

I'll try apply all these latest mods and see if it helps solve my problems.

/J

Michael Jones wrote:
> Hello,
> 
> After some serious head banging I found this little peace of DNA at the site
> of the crime: "...{.R1-*}{.R1-*}{.RS.O.O.O..." - The forensic lab was in
> tumult...
> 
> With this little sequence it was possible to locate the exact spot of the
> crime and take some quite distinct fingerprints (see:
> http://private.l-s-b.de:81/evidence.png).
> 
> 
> 
> The simplest way to "fix" this (for verification of problem only) is:
> 
> int NutEventWait(volatile HANDLE * qhp, u_long ms)
> {
>     NUTTHREADINFO *tdp;
>     
>     /* Get the queue's root atomically. */
> 
>     NutEnterCritical();		// <===================== Patch
>     tdp = *qhp;
> 
>     /*
>      * Check for posts on a previously empty queue. 
>      */
>     if (tdp == SIGNALED) {
>         /*
>          * Even if already signaled, switch to any other thread, which 
>          * is ready to run and has the same or higher priority.
>          */
>         *qhp = 0;
> 	  NutExitCritical();	// <===================== Patch
>         
>         NutThreadYield();
>         return 0;
>     }
>     /*
>      * Remove the current thread from the list of running threads 
>      * and add it to the specified queue.
>      */
>     NutThreadRemoveQueue(runningThread, &runQueue);
>     NutThreadAddPriQueue(runningThread, (NUTTHREADINFO **) qhp);
> 
>     NutExitCritical();		// <===================== Patch
> 
> 	.
> 	.
> 	.
> 
> But, as the problem is in NutThreadAddPriQueue(...) I propose the following
> less Critical-Section intensive version (which possibly can be further
> refined):
> 
> void NutThreadAddPriQueue(NUTTHREADINFO * td, NUTTHREADINFO * volatile
> *tqpp)
> {
>     NUTTHREADINFO *tqp;
> 
>     td->td_queue = (HANDLE) tqpp;
>     td->td_qpec = 0;			// start with clean event count
> 
>     NutEnterCritical();
>     tqp = *tqpp;
> 
>     if (tqp == SIGNALED) {
>         tqp = 0;
>         td->td_qpec++;			// transfer the signaled state 
>     } else if (tqp) {
>         NutExitCritical();		// there are other threads in queue
> 						// so its save to leave
> critical.          
> 
>         while (tqp && tqp->td_priority <= td->td_priority) {
>             tqpp = &tqp->td_qnxt;
>             tqp = tqp->td_qnxt;
>         }
> 
>         NutEnterCritical();		// back into critical
>     }
> 
>     td->td_qnxt = tqp;
> 
>     *tqpp = td;
>     if (td->td_qnxt && td->td_qnxt->td_qpec) {
>         td->td_qpec += td->td_qnxt->td_qpec; // don't overwrite count
>         td->td_qnxt->td_qpec = 0;
>     }
>     NutExitCritical();
> }
> 
> With this change I feel confident that we have finally got to the bottom of
> the problem! Bashing the OS with massive amounts of ARP & Random packets
> (about 25% utilization of 100Mbps) has virtually no effect any more - just
> the to be expected decrease of throughput (actually one of our Linux
> machines stopped dead during the test - probably something that it ate).
> 
> 
> 
> Cu,
> Michael
> 
> 
> 
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> 
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