The patch titled
lock validator: netlink.c netlink_table_grab fix
has been removed from the -mm tree. Its filename is
lock-validator-netlinkc-netlink_table_grab-fix.patch
This patch was probably dropped from -mm because
it has now been merged into a subsystem tree or
into Linus's tree, or because it was folded into
its parent patch in the -mm tree.
------------------------------------------------------
Subject: lock validator: netlink.c netlink_table_grab fix
From: Frederik Deweerdt <deweerdt@xxxxxxx>
ipw2200 calls netlink_broadcast from irq context.
this isn't allow to be called from IRQ context, because it takes
nl_table_lock for read, but that is taken as
write_lock_bh(&nl_table_lock);
in
static void netlink_table_grab(void)
so without disabling interrupts; which would thus deadlock if this
read_lock-from-irq would hit.
> <c02fb6a4> wireless_send_event+0x304/0x340
> <e1cf8e11> ipw_rx+0x1371/0x1bb0 [ipw2200]
> <e1cfe6ac> ipw_irq_tasklet+0x13c/0x500 [ipw2200]
> <c0121ea0> tasklet_action+0x40/0x90
but it's more complex than that, since we ARE in BH context.
The complexity comes from us holding &priv->lock, which is
used in hard irq context.
so the deadlock is like this:
cpu 0: user context cpu1: softirq context
netlink_table_grab takes nl_table_lock as take priv->lock in ipw_irq_tasklet
write_lock_bh, but leaves irqs enabled
hardirq comes in and the isr tries to take in ipw_rx, call wireless_send_event which
priv->lock but has to wait on cpu 1 tries to take nl_table_lock for read
but has to wait for cpu0
and... kaboom kabang deadlock :)
(akpm: it's not clear that this is the right fix?)
Signed-off-by: Frederik Deweerdt <frederik.deweerdt@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxx>
Cc: "Zhu, Yi" <yi.zhu@xxxxxxxxx>
Cc: Jeff Garzik <jeff@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
net/netlink/af_netlink.c | 8 ++++----
1 files changed, 4 insertions(+), 4 deletions(-)
diff -puN net/netlink/af_netlink.c~lock-validator-netlinkc-netlink_table_grab-fix net/netlink/af_netlink.c
--- 25/net/netlink/af_netlink.c~lock-validator-netlinkc-netlink_table_grab-fix Fri Jun 2 15:10:18 2006
+++ 25-akpm/net/netlink/af_netlink.c Fri Jun 2 15:10:18 2006
@@ -157,7 +157,7 @@ static void netlink_sock_destruct(struct
static void netlink_table_grab(void)
{
- write_lock_bh(&nl_table_lock);
+ write_lock_irq(&nl_table_lock);
if (atomic_read(&nl_table_users)) {
DECLARE_WAITQUEUE(wait, current);
@@ -167,9 +167,9 @@ static void netlink_table_grab(void)
set_current_state(TASK_UNINTERRUPTIBLE);
if (atomic_read(&nl_table_users) == 0)
break;
- write_unlock_bh(&nl_table_lock);
+ write_unlock_irq(&nl_table_lock);
schedule();
- write_lock_bh(&nl_table_lock);
+ write_lock_irq(&nl_table_lock);
}
__set_current_state(TASK_RUNNING);
@@ -179,7 +179,7 @@ static void netlink_table_grab(void)
static __inline__ void netlink_table_ungrab(void)
{
- write_unlock_bh(&nl_table_lock);
+ write_unlock_irq(&nl_table_lock);
wake_up(&nl_table_wait);
}
_
Patches currently in -mm which might be from deweerdt@xxxxxxx are
lock-validator-netlinkc-netlink_table_grab-fix.patch
acpi-identify-which-device-is-not-power-manageable-fix.patch
-
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