From owner-freebsd-scsi  Mon Jan 15 17:27: 8 2001
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Date: Mon, 15 Jan 2001 17:26:48 -0800 (PST)
From: Matthew Jacob <mjacob@feral.com>
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To: freebsd-scsi@freebsd.org, alpha@freebsd.org
Subject: huh... watch out for overflows...
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This construct is fairly common in CAM drivers:

	timeout(XXXX, YYYYY,  (ccb->ccb_h.timeout * hz)/1000);

The problem here is that timeout is u_int32_t and that some platforms have a
high hz rate (1024 on some alphas, e.g.).

If you take the normal tape timeout of two hours for an I/O operation, and
keeping in mind that timeout is in milliseconds, you overflow 32 bits, thus
leading to a timeout with a somewhat unpredictable (but surely wrong) value.

-matt






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