Re: [PATCH] Fix SMP support on 3c527 net driver
From: Manfred Spraul
Date: Sun Aug 31 2003 - 03:29:43 EST
Felipe wrote:
Also, the down/up function doesn't seem to be
used in interrupt context, so I think it will work.
[snip]
static int mc32_send_packet(struct sk_buff *skb, struct net_device *dev)
{
struct mc32_local *lp = (struct mc32_local *)dev->priv;
- unsigned long flags;
volatile struct skb_header *p, *np;
netif_stop_queue(dev);
- save_flags(flags);
- cli();
+ down(&lp->mc32_sem);
No, that's wrong. mc32_send_packet is the hard_start_xmit function,
called from bottom half context, with the dev_xmit_lock spinlock held.
Additionally, you must replace the sleep_on calls with wait_event, or an
open-coded wait queue: sleep_on is racy, it only works with cli().
IMHO the right way to fix cli() is
- add a single spinlock to the driver or the device structure. Do not
forget the spin_lock_init().
- replace cli/sti with spin_lock_irqsave/spin_unlock_irqsave.
- Additionally acquire the spinlock in every interrupt handler (cli()
stops all interrupts, spinlocks only stop interrupt on the current cpu).
- check if there were recursive cli() calls. Fix them.
- replace all sleep_on calls with wait queue calls.
- check if there are any kmalloc or schedule calls in the area now under
the spinlock, and reorganize the code.
And please add a changelog entry that code was converted without testing.
--
Manfred
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