Re: [9front] Re: [PATCH] devproc: use the correct limit when warning that conf.nproc is too high

[ori@eigenstate.org]

Quoth Anthony Martin <ality@pbrane.org>:
> james palmer <james@biobuf.link> once said:
> > -	if(conf.nproc >= (1<<(16-QSHIFT))-1)
> > +	if(conf.nproc >= (1<<23)-1)
> 
> This change could be better. Skip to the end for the patch or
> continue reading for a stroll down memory lane.
> 
> The number of qid types in the proc(3) file system has slowly
> increased over time. The first edition originally had nine:
> 
> 	Qdir, Qctl, Qmem, Qnote, Qnotepg, Qproc, Qsegment, Qstatus,
> 	and Qtext.
> 
> The second edition added two:
> 
> 	Qnoteid, and Qwait.
> 
> The third edition added six:
> 
> 	Qfd, Qfpregs, Qkregs, Qns, Qregs, and Qprofile.
> 
> The fourth edition added three:
> 
> 	Qargs in 2002, Qtrace in 2003, and Qsyscall in 2010.
> 
> And 9front has added two more:
> 
> 	Qppid in 2011, and Qwatchpt in 2017.
> 
> The number surpassed 16 in 3ed so QSHIFT was incremented and the
> constants were adjusted but, unfortunately, the comment was not
> updated at that time.
> 
> In May 2011, quanstro pointed this out on 9fans and it was corrected.
> The QID and SLOT macros were also changed to calculate the mask based
> on QSHIFT. The guard testing for too many procs in procinit was also
> fixed.
> 
> This change happened shortly after the 9front fork happened so it was
> easily missed.
> 
> Cheers,
>   Anthony
> 
> % cd /n/dump/2011
> % diff -c (0526 0527)^/sys/src/9/port/devproc.c
> 0526/sys/src/9/port/devproc.c:132,139 - 0527/sys/src/9/port/devproc.c:132,139
> 
>   /*
>    * Qids are, in path:
> -  *	 4 bits of file type (qids above)
> -  *	23 bits of process slot number + 1
> +  *	 5 bits of file type (qids above)
> +  *	26 bits of process slot number + 1
>    *	     in vers,
>    *	32 bits of pid, for consistency checking
>    * If notepg, c->pgrpid.path is pgrp slot, .vers is noteid.
> 0526/sys/src/9/port/devproc.c:140,147 - 0527/sys/src/9/port/devproc.c:140,147
>    */
>   #define	QSHIFT	5	/* location in qid of proc slot # */
> 
> - #define	QID(q)		((((ulong)(q).path)&0x0000001F)>>0)
> - #define	SLOT(q)		(((((ulong)(q).path)&0x07FFFFFE0)>>QSHIFT)-1)
> + #define	QID(q)		((((ulong)(q).path) & ((1<<QSHIFT)-1)) >> 0)
> + #define	SLOT(q)		(((((ulong)(q).path) & ~(1UL<<31)) >> QSHIFT) - 1)
>   #define	PID(q)		((q).vers)
>   #define	NOTEID(q)	((q).vers)
> 
> 0526/sys/src/9/port/devproc.c:288,294 - 0527/sys/src/9/port/devproc.c:288,294
>   static void
>   procinit(void)
>   {
> - 	if(conf.nproc >= (1<<(16-QSHIFT))-1)
> + 	if(conf.nproc >= (1<<(31-QSHIFT))-1)
>   		print("warning: too many procs for devproc\n");
>   	addclock0link((void (*)(void))profclock, 113);	/* Relative prime to HZ */
>   }
> %
> 

Yeah, that looks better. Thanks for digging it up;
applying it by hand.

As a side note, 'diff -u' or 'ape/diff -u' makes for a
patch that can be applied directly from email:

	ape/patch -p1 </mail/fs/mbox/51913/body