On 05/04/2016 04:27 PM, Julio Guerra wrote: >>> When a tty (here a slave pty) is set in noncanonical input and blocking read modes, a read() randomly blocks when: >>> "VMIN > kernel received >= user buffer size > 0". >>> >>> The standard says that read() should block until VMIN bytes are received [1][2]. Whether this is an implementation defined case not really specified by POSIX or not, it should not behave randomly (otherwise it really should be documented in termios manpage). >> >> This is not a bug. >> >> From the termios(3) man page: >> >> * MIN > 0; TIME == 0: read(2) blocks until the lesser of MIN bytes or the number of bytes requested are avail‐ >> able, and returns the lesser of these two values. >> > > This does not appear in my man... > > Anyway, how do you explain the random behavior then? A long standing bug in this read mode allows the asynchronous input processing thread to race with the read() thread and become confused about how much data remains. I fixed this in 4.6; when I run your test on 4.6, it consistently returns the full user buffer. Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
