Messages in this thread Patch in this message | | | Date | Fri, 20 Apr 2007 16:15:51 +0200 | From | Jan Yenya Kasprzak <> | Subject | Re: [PATCH 1/3] Char: mxser_new, fix recursive locking |
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Alan Cox wrote: : > Acquire a port lock only if not in_interrupt in some places, because ISR : > holds the lock yet (and ldisc calls some of driver's routines which tries to : > acquire it again due to tty->low_latency). : : NAK : : This is the wrong way to do it. If you don't support recursive entry then : don't use ->low_latency. If you do then ensure you drop the lock before : you call tty_flip_buffer_push().
I did as you suggested, and I am not able to reproduce the problem now. The patch is attached. I think it is quite minimal, so it should be safe to apply it. What do you think, Jiri?
Signed-off-by: Jan "Yenya" Kasprzak <kas@fi.muni.cz> Cc: Jiri Slaby <jirislaby@gmail.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
--- linux-2.6.21-rc2/drivers/char/mxser_new.c.orig 2007-04-20 15:41:46.000000000 +0200 +++ linux-2.6.21-rc2/drivers/char/mxser_new.c 2007-04-20 15:46:46.000000000 +0200 @@ -2230,7 +2230,14 @@ port->mon_data.rxcnt += cnt; port->mon_data.up_rxcnt += cnt; + /* + * We are called from an interrupt context with &port->slock + * being held. Drop it temporarily in order to prevent + * recursive locking. + */ + spin_unlock(&port->slock); tty_flip_buffer_push(tty); + spin_lock(&port->slock); } static void mxser_transmit_chars(struct mxser_port *port)
-Yenya
-- | Jan "Yenya" Kasprzak <kas at {fi.muni.cz - work | yenya.net - private}> | | GPG: ID 1024/D3498839 Fingerprint 0D99A7FB206605D7 8B35FCDE05B18A5E | | http://www.fi.muni.cz/~kas/ Journal: http://www.fi.muni.cz/~kas/blog/ | > I will never go to meetings again because I think face to face meetings < > are the biggest waste of time you can ever have. --Linus Torvalds < - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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