Date: Tue, 21 Aug 2001 04:29:15 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: Christian Weisgerber <naddy@mips.inka.de> Cc: freebsd-alpha@freebsd.org Subject: Re: alpha problems on current Message-ID: <3B82460B.7DA88A3F@mindspring.com> References: <20010817081929.A2859@freebie.xs4all.nl> <20010817152742.B437@cicely20.cicely.de> <9lje5o$24ra$1@kemoauc.mips.inka.de> <20010818172224.A4918@cicely20.cicely.de> <9ln48d$1ml6$1@kemoauc.mips.inka.de>
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Christian Weisgerber wrote: > > > > > - I'm seeing mysterious writes (kevent says NOTE_WRITE) to my > > > > > executables. I suspect this is a VM bug. > > > > Have you found a way to isulate when it happens? > > No. I wrote a little program that watches /bin/* through kevent(2), > but I'm uncertain how to trace this any further. The writes don't > appear to be related to any particular system activity, although > they possibly correlate with the amount of activity. Also, if I > don't run setiathome in the background I get far fewer writes. > > The only strange program crash I've seen so far has been an xlogout > dying with SEGV. What are you running in your crontab? There's a well known historical problem in VM that was often tickled by the copy on write that happens with the mmap'ed database file being modified; the Vixie cron program "updates" the record in place, which triggers this. It does the update on the (now incorrect) assumption that the pwent that it gets back is actually a pointer to a static data area in libc. I thought that this bug had been squashed a year ago, but it may be that it just went into hiding. On 3.x and early 4.x, it exhibited as a random write of a page worth of the database being spammed on top of a random file (usually, it spammed the crontab itself, but I've seen it spam other files, as well). As a hack, try killing cron, and see if it still happens; if it does, then you've at least eliminated my prime suspect. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message
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