I could not find the original specification of this standard, although
many proprietary implementations exist (or claim to exist). Also there
are many 3rd-party descriptions of the method, which often differ in one
or another detail, but after some reading I could conclude that the most
likely definition should be as follows:
1. Fill the device with zeroes, do not verify.
2. Fill the device with ones, do not verify.
3. Fill the device with a PRNG stream, do verify.
In other words, this is a simplified version of nwipe's "dodshort".
Symptoms: If you control-C to exit nwipe at the end of a successful
wipe you would get a segmentation fault. If nwipe log data was being
sent to stdout rather than to a log file, then you would not see the
log in the terminal windows after nwipe had exited. This patch fixes
those problems by creating a tri-state wipe flag for each wipe
thread. The main thread after having launched the wipe threads
will wait for ALL wipe flags to report that the wipe routine has
completed and the thread has exited. Only at that time does the
main() routine then proceed with joining the threads and waiting
for the join to confirm the thread has indeed exited. This join
is important as the thread will not actually exit until the OS
has flushed the disk buffers. Currently nwipe does not use O_SYNC
where data is sent straight to disk. Therefore it's important
to wait for data to be flushed before exiting nwipe. Part of this
patch is introducing a "please wait .. disks are being flushed"
prior to exiting nwipe otherwise it might look like nwipe had
hung. A disk flush in terms of how long it takes, can be from
instantly to 30 seconds or more, depending on how much system
memory you have, when the last sync occurred and if you have
changed the sync option from it's default. Something else to
note is that when all wipes have finished nwipe displays "Enter
To Exit" on the status line at the bottom of the screen. I
believe typing 'enter' rather than control-c did not produce a
segmentation fault. Irrespective, both methods of exiting nwipe
have been tested and confirmed to now work correctly. Tested
overnight with two drives using multiple wipe methods,
verification and blanking.
