Messages in this thread | | | Date | Mon, 12 Jun 2017 14:04:54 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [RFC, PATCH] imx: serial: Take tty->files_lock opportunistically |
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On Mon, Jun 12, 2017 at 08:55:44AM -0300, Fabio Estevam wrote: > Hi Greg, > > On Mon, Jun 12, 2017 at 3:46 AM, Greg Kroah-Hartman > <gregkh@linuxfoundation.org> wrote: > > >> linux-next is good, but mainline is not. > >> > >> Actually we need 4dec2f119e86f9c9 ("imx-serial: RX DMA startup > >> latency") to be applied to 4.12-rc as well. > > > > Why? Can't it wait until 4.13-rc1? > > Because without 4dec2f119e86f9c9 the imx serial driver behaves badly > in 4.12-rc. > > Just tested 4.12-rc5 and there is scary verbose warning: > > [ 11.714904] ===================================================== > [ 11.721006] WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected > [ 11.727628] 4.12.0-rc5 #413 Not tainted > [ 11.731470] ----------------------------------------------------- > [ 11.737572] rawtest/219 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: > [ 11.744018] (&(&tty->files_lock)->rlock){+.+...}, at: [<c04d83a0>] > imx_startup+0x2c4/0x510 > [ 11.752403] > [ 11.752403] and this task is already holding: > [ 11.758241] (&port_lock_key){-.....}, at: [<c04d81e8>] > imx_startup+0x10c/0x510 > [ 11.765571] which would create a new lock dependency: > [ 11.770626] (&port_lock_key){-.....} -> (&(&tty->files_lock)->rlock){+.+...} > [ 11.777791] > [ 11.777791] but this new dependency connects a HARDIRQ-irq-safe lock: > [ 11.785712] (&port_lock_key){-.....} > [ 11.785726] > .... > > Complete stack at: https://pastebin.com/a2gUTwZK > > This problem is caused by commit 18a4208826dd0 ("imx-serial: Reduce RX > DMA startup latency when opening for reading"). > > linux-next has a fix for it: 4dec2f119e86f9c9 ("imx-serial: RX DMA > startup latency") > > Applying 4dec2f119e86f9c9 ("imx-serial: RX DMA startup latency") into > 4.12-rc5 makes the issue go away.
Ok, if I end up with some more tty/serial fixes for 4.12-final, I'll consider queueing this one up as well, thanks.
greg k-h
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