arch/sim: set stdin/stdout nonblocking in host_uart_start() - #20032
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to avoid the blocking indefinitely when the host uart is not ready to read/write data. Signed-off-by: chenzihan1 <chenzihan1@xiaomi.com>
When NuttX sim is connected via pipe (e.g. by an automation tool), if the host side does not read stdout in time, the pipe buffer fills up and write(1, ...) blocks the entire sim process. This happens inside host_uninterruptible (irq disabled), so the NuttX scheduler is completely frozen and all threads stop. Set fd=1 (stdout) to O_NONBLOCK so that write() returns EAGAIN instead of blocking. The TX data stays in the NuttX xmit buffer and sim_tty_work retries every 1ms until the pipe has space. Signed-off-by: ligd <liguangdi1@xiaomi.com>
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Update host_uart_start() to set stdin/stdout nonblocking via ioctl. Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
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Summary
ioctl(FIONBIO)inhost_uart_start().write(1, ...)blocks the entire sim process. This happens insidehost_uninterruptible(irq disabled), so the NuttX scheduler is completely frozen and all threads stop.write()returnsEAGAINinstead; the TX data stays in the NuttX xmit buffer andsim_tty_workretries every 1ms until the pipe has space.Impact
arch/sim/src/sim/posix/sim_hostuart.c), no functional change for interactive terminal usage.Testing
Built and booted
sim:nshon Linux, console I/O works as before; verified the sim no longer freezes when stdout is a pipe that is not drained by the reader.