Date: Thu, 28 Jan 1999 13:22:06 +1100 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, dgilbert@velocet.net Cc: security@FreeBSD.ORG Subject: Re: signal handling in urandom can cause lockup Message-ID: <199901280222.NAA20754@godzilla.zeta.org.au>
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> This is very interesting. For some time (I use FreeBSD on my >desktop as well as for 50 odd servers) my desktop machine has been >exhibiting a freeze that seems to coinside with intense swapping or >writing to the disk. This 'freeze' survived the upgrade from 2.2.7 to >3.0. > Now... my take on the situation had been that IDE is just >evil. I have burned out 3 drives (of different brands) in as many >months (they ranged from 1 month to 1 year old). I have on order a 9G >SCSI drive to become the main system and swap drive under the >assumption that scsi drives are going to be more dependable and will >not freeze the system. I have no problems with IDE, and this problem has very little to do with IDE. It is a general problem with devices that can transfer large amounts of data without blocking (not just with slow devices like I said before, except faster devices tend to limit the denial of service to a second or two). E.g., a modern IDE drive can transfer at a rate of 12-15MB/sec. The default interface is 16-bit PIO mode 1-4 (where the BIOS decides the mode number). At best, this transfers data at 8.3MB/sec and takes 100% of the CPU to do so. Don't connect a modern IDE drive to this interface. > However, it does strike me as bogus that this kind of blocking >happens. Maybe this type of patch should be applied to devices in >general. It already applies to everything that calls uiomove(), including many cases involving filesystem i/o. It doesn't apply to paging or certain optimised filesystem i/o. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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