Serial driver lockup

Question

Serial driver lockup

opened this issue 15 years ago · comments

Deleted user commented 15 years ago

This command sequence locks up the serial driver:

echo test > /dev/ttyS0 # works fine
echo test > /dev/ttyS0 # lockup!

Takeshi MATSUYA · Answer 1 · Tue Feb 23 2010 10:42:57 GMT+0800 (China Standard Time)

Which config file did you use ?

Deleted user · Answer 2 · Sat Mar 06 2010 02:06:05 GMT+0800 (China Standard Time)

ml401 vga defconfig, and an inittab that does not put a getty on the serial port.

Problem is still present as of today.

Takeshi MATSUYA · Answer 3 · Sat Mar 06 2010 17:29:06 GMT+0800 (China Standard Time)

I could not confirm the problem.
Could you show me the results of following commands?

stty 115200 </dev/ttyS0
echo hello >/dev/ttyS0
cat /etc/inittab

Takeshi MATSUYA · Answer 4 · Wed Mar 10 2010 20:06:52 GMT+0800 (China Standard Time)

lekernel wrote:
Problem only appears at lower speeds (9600 bps for example) and not in QEMU. This suggests a race condition.

stty 9600 < /dev/ttyS0
echo test > /dev/ttyS0
echo test > /dev/ttyS0

causes the problem on the board with apparently 100% reproducibility.

Also, when you send a long string at 115200bps, the serial driver crashes with "huh, entered softirq 6 TASKLET 40030150 preempt_count 00000100, exited with 4381fd50? BUG: scheduling while atomic"

( I have deleted this comment by mistake. )