threads/103127: Kernel panic while using thread features in Squid 2.6

[Anders Nordby]

The following reply was made to PR kern/103127; it has been noted by GNATS.

From: Anders Nordby <anders at fupp.net>
To: FreeBSD-gnats-submit at FreeBSD.org, freebsd-threads at FreeBSD.org
Cc: Suleiman Souhlal <ssouhlal at FreeBSD.org>,
	Pawel Worach <pawel.worach at gmail.com>,
	Thomas-Martin Seck <tmseck at netcologne.de>
Subject: Re: threads/103127: Kernel panic while using thread features in Squid 2.6
Date: Wed, 13 Sep 2006 20:58:03 +0200

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 Content-Disposition: inline
 
 Hi,
 
 After talking with Pawel, I tried the attached patch to get some kqueue
 debug info. I just got it:
 
 Sep 13 20:18:56 cache3 kernel: NULL f_event in new kn
 Sep 13 20:18:56 cache3 kernel: f_event == NULL
 
 Then Squid stops responding to new requests, and I can not even kill it
 with kill -9:
 
 root at cache3:~# pgrep -l squid
 547 squid
 root at cache3:~# kill -9 547
 root at cache3:~# pgrep -l squid
 547 squid
 
 Have to reboot to get the system working again, but it seems now it
 doesn't panic.
 
 Regards,
 
 -- 
 Anders.
 
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 Content-Disposition: attachment; filename="kqueue-debug.patch"
 
 --- sys/kern/kern_event.c.orig	Wed Sep 13 08:44:57 2006
 +++ sys/kern/kern_event.c	Wed Sep 13 08:51:03 2006
 @@ -900,6 +900,8 @@
  				goto done;
  			}
  			KN_LIST_LOCK(kn);
 +			if (kn->kn_fop->f_event == NULL)
 +				printf("NULL f_event in new kn\n");
  		} else {
  			/*
  			 * The user may change some filter values after the
 @@ -912,6 +914,8 @@
  			kn->kn_sfflags = kev->fflags;
  			kn->kn_sdata = kev->data;
  			kn->kn_kevent.udata = kev->udata;
 +			if (kn->kn_fop->f_event == NULL)
 +				printf("NULL f_event in existing kn\n");
  		}
  
  		/*
 @@ -921,6 +925,12 @@
  		 * is called on a zombie process.  It will call filt_proc
  		 * which will remove it from the list, and NULL kn_knlist.
  		 */
 +		if (kn->kn_fop->f_event == NULL) {
 +			printf("f_event == NULL\n");
 +			KN_LIST_UNLOCK(kn);
 +			error = EAGAIN;
 +			goto done;
 +		}
  		event = kn->kn_fop->f_event(kn, 0);
  		KQ_LOCK(kq);
  		if (event)
 
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