Misleading error messages from blktrace
Posted: Sat, 12 November 2011 | permalink | No comments
If you ever get an error message from the blktrace tool that looks like
this:
BLKTRACESETUP(2) /dev/dm-0 failed: 2/No such file or directory
Thread 3 failed open /sys/kernel/debug/block/(null)/trace3: 2/No such file or directory
Thread 2 failed open /sys/kernel/debug/block/(null)/trace2: 2/No such file or directory
Thread 0 failed open /sys/kernel/debug/block/(null)/trace0: 2/No such file or directory
Thread 1 failed open /sys/kernel/debug/block/(null)/trace1: 2/No such file or directory
FAILED to start thread on CPU 0: 1/Operation not permitted
FAILED to start thread on CPU 1: 1/Operation not permitted
FAILED to start thread on CPU 2: 1/Operation not permitted
FAILED to start thread on CPU 3: 1/Operation not permitted
Don’t be alarmed – your disk hasn’t suddenly disappeared out from
underneath you. In fact, it means quite the opposite of what “No such file
or directory” might imply. In fact, it means that there is already a
blktrace of that particular block device in progress, and you’ll need to
kill that one off before you can start another one.
Thank $DEITY for the kernel source code – it was the only hope I had of diagnosing this particular nit before I went completely bananas and smashed my keyboard into small pieces.
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