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Date: Fri, 25 Sep 2009 21:23:12 +0800
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From: Rohit Grover <rgrover1@gmail.com>
To: freebsd-current@freebsd.org
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Subject: hald spins in a poll/read loop against /dev/usb with CURRENT
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Hald spins endlessly on my CURRENT. I have the following from truss:

open("/dev/usb",O_RDONLY,00)                     = 12 (0xc)
...
...
poll({4/POLLIN 8/POLLIN 10/POLLIN|POLLPRI 15/POLLIN 89/POLLIN 6/POLLIN
9/POLLIN 88/POLLIN 7/POLLIN 12/POLLIN},10,161) = 1 (0x1)
gettimeofday({1253883730.961100 },0x0)           = 0 (0x0)
read(12,0xbfbfe56c,384)                          = 0 (0x0)
gettimeofday({1253883730.961158 },0x0)           = 0 (0x0)
poll({4/POLLIN 8/POLLIN 10/POLLIN|POLLPRI 15/POLLIN 89/POLLIN 6/POLLIN
9/POLLIN 88/POLLIN 7/POLLIN 12/POLLIN},10,161) = 1 (0x1)
gettimeofday({1253883730.961228 },0x0)           = 0 (0x0)
read(12,0xbfbfe56c,384)                          = 0 (0x0)
gettimeofday({1253883730.961286 },0x0)           = 0 (0x0)
poll({4/POLLIN 8/POLLIN 10/POLLIN|POLLPRI 15/POLLIN 89/POLLIN 6/POLLIN
9/POLLIN 88/POLLIN 7/POLLIN 12/POLLIN},10,161) = 1 (0x1)
gettimeofday({1253883730.961357 },0x0)           = 0 (0x0)
read(12,0xbfbfe56c,384)                          = 0 (0x0)
gettimeofday({1253883730.961415 },0x0)           = 0 (0x0)
...
...

Why is /dev/usb responding to poll() when there is no data to be read?

thanks.