The following reply was made to PR kern/36673; it has been noted by GNATS.

From: Juan RP <juan@xtrarom.org>
To: gnats-bugs@NetBSD.org
Cc: yamt@mwd.biglobe.ne.jp (YAMAMOTO Takashi)
Subject: Re: kern/36673 (dubious code is sysmon_envsys)
Date: Tue, 24 Jul 2007 01:35:30 +0200

 On Mon, 23 Jul 2007 23:20:03 +0000 (UTC)
 yamt@mwd.biglobe.ne.jp (YAMAMOTO Takashi) wrote:
 
 >  the usages of these mutexes are not obvious or documented.
 >  
 >  for example,
 >  - i can't understand why sysmon_envsys_createplist acquires
 >   sme_mtx in the loop.
 
 I wanted to protect the sme_gtredata function callback, this one
 is executed in the driver to refresh data in the sensors.
 
 >  - sysmon_envsys_register seems to assume sysmon_envsys_list is stable
 >   while unlocking sme_list_mtx.
 
 Do you think the following patch is ok for you?
 
 Index: sysmon_envsys.c
 ===================================================================
 RCS file: /cvsroot/src/sys/dev/sysmon/sysmon_envsys.c,v
 retrieving revision 1.43
 diff -b -u -r1.43 sysmon_envsys.c
 --- sysmon_envsys.c	23 Jul 2007 17:51:16 -0000	1.43
 +++ sysmon_envsys.c	23 Jul 2007 23:30:18 -0000
 @@ -483,7 +483,6 @@
  	mutex_enter(&sme_list_mtx);
  	LIST_FOREACH(lsme, &sysmon_envsys_list, sme_list) {
  	       if (strcmp(lsme->sme_name, sme->sme_name) == 0) {
 -		       mutex_exit(&sme_list_mtx);
  		       error = EEXIST;
  		       goto out;
  	       }
 @@ -496,16 +495,14 @@
  	sme->sme_fsensor = sysmon_envsys_next_sensor_index;
  	sysmon_envsys_next_sensor_index += sme->sme_nsensors;
  #endif
 -	mutex_exit(&sme_list_mtx);
  	error = sysmon_envsys_createplist(sme);
  	if (!error) {
 -		mutex_enter(&sme_list_mtx);
  		LIST_INSERT_HEAD(&sysmon_envsys_list, sme, sme_list);
  		sme_uniqsensors = 0;
 -		mutex_exit(&sme_list_mtx);
  	}
  
  out:
 +	mutex_exit(&sme_mtx);
  	return error;
  }
  
 @@ -626,6 +623,9 @@
  
  	nsens = error = 0;
  
 +	KASSERT(mutex_owned(&sme_list_mtx));
 +	mutex_exit(&sme_list_mtx);
 +
  	/* create the sysmon envsys device array. */
  	array = prop_array_create();
  	if (array == NULL)
 
 
 One thing that is not clear to me is if I can allocate/deallocate memory
 with a mutex held, can you please answer?
 
 -- 
 Juan Romero Pardines 	- The NetBSD Project
 http://plog.xtrarom.org 	- NetBSD/pkgsrc news in Spanish