Messages in this thread | | | Date | Thu, 26 Oct 2017 15:31:55 +0100 | From | Alan Cox <> | Subject | Re: [PATCH] tty: fix flush_to_ldisc() oops before tty_open is done |
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> I can reproduce this problem on CentOS now. It seems better to leave this problem to drivers, not the user process. > Do you think we should examine serial drivers of ARM, like pl011?
Can you reproduce it on real hardware - I ask because the driver has been around for years without reports and it would be good to know it's not a virtual platform problem you are chasing.
> --------------------------------------------------------------------------------------- > Does it means this serial driver do not support activate/deactive? Is that out of date? > Because tty driver is complex, I am studying the concept and source code, and need time to find a good solution.
AMBA uses the uart layer. So uart does a lot of the work.
Yes the driver is complex and the core hangup/receive paths are tricky to understand. The open path however is fairly simple so the fact you see a failure there makes me suspicious and I tink that is the first one to trace because the tty_open paths do not set port->tty until the tty is initialized properly.
The hangup path is complex and has a history of bugs and races so is a bit less surprising.
The important detail here is that both the queueing of data and the hangup are done by schedule_work() and as far as I can see (the code has changed somewhat since I last dug into that bit) rely on that to avoid the two executing at the same time.
Alan
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