Hi, I'm currently testing a RT application that communicates with sensor hardware using a tty serial port. The application polls the tty port (non-blocking) in a user space thread (priority 80) for incoming data. On a raspberry PI3 (ttyAMA0), with kernel 4.4.9-rt17, response times < 650usec are achieved, which is fine. Any version equal or above 4.4.12-rt20 will increase response peaks to (about 0.1%) > 2msec, with some peaks > 5msec. cyclictest doesn't reproduce this, so I suspected a change in the tty driver, or related to raspberry pi. I found that, by reverting the attached patch, response times return to < 650usec. I suspect it has something to do with a change in the read poll. I'd like to help solving this issue, can anyone give me some pointers on how to continue? Regards, Niels Kolthoff
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Fix OpenSSH pty regression on close.patch
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