Make kdb CONFIG_LOCKDEP friendly.
Use of a serial line console with kdb and lockdep enabled
generates lots of lockdep warnings on kdb/entry edit.
So fix the circular locking dependency between the
kdb_printf and the 8250's port->lock, by suppressing all
use of port->lock by the 8250 serial driver when kdb_printf
is active.
This means that the allowed locking direction is:
port->lock ---> kdb_printf_lock
Signed-off-by: Joe Korty <[email protected]>
Index: 2.6.31.3-kdb/kdb/kdb_io.c
===================================================================
--- 2.6.31.3-kdb.orig/kdb/kdb_io.c 2009-10-12 11:05:01.000000000 -0400
+++ 2.6.31.3-kdb/kdb/kdb_io.c 2009-10-12 11:06:50.000000000 -0400
@@ -540,6 +540,7 @@
} else {
__acquire(kdb_printf_lock);
}
+ atomic_inc(&kdb_8250);
diag = kdbgetintenv("LINES", &linecount);
if (diag || linecount <= 1)
@@ -774,6 +775,7 @@
if (logging) {
console_loglevel = saved_loglevel;
}
+ atomic_dec(&kdb_8250);
if (KDB_STATE(PRINTF_LOCK) && got_printf_lock) {
got_printf_lock = 0;
spin_unlock_irqrestore(&kdb_printf_lock, flags);
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