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 <[email protected]>
Cc: Jiri Slaby <[email protected]>
Cc: Alan Cox <[email protected]>
--- 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/ |
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> are the biggest waste of time you can ever have. --Linus Torvalds <
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