Re: [PATCH 2/2] ehea: fix mutex and spinlock use

From: Sebastien Dugue
Date: Tue Sep 16 2008 - 02:58:20 EST

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On Mon, 15 Sep 2008 17:18:27 +0200 Thomas Klein <osstklei@xxxxxxxxxx> wrote:

> NACK!
>
> I regret but this patch is wrong. It is not sufficient to only lock
> the replacement of an old list with a new list. Building up those
> lists is a 3-step process:
>
> 1. Count the number of entries a list will contain and allocate mem
> 2. Fill the list
> 3. Replace old list with updated list
>
> It's obvious that the contents of the list may not change during this
> procedure. That means that not only the list build-up procedure must
> be locked. It must be assured that no function that modifies the list's
> content can be called while another list update is in progress.
>
> Jeff, please revert this patch.

OK, your call, you know the code better than I do.

But the locking could at least be pushed into ehea_update_firmware_handles()
and ehea_update_bcmc_registrations() instead of being at each call site.

Thanks,

Sebastien.

>
> Thanks
> Thomas
>
>
>
> Sebastien Dugue wrote:
> > Looks like to me that the ehea_fw_handles.lock mutex and the
> > ehea_bcmc_regs.lock spinlock are taken much longer than necessary and could
> > as well be pushed inside the functions that need them
> > (ehea_update_firmware_handles() and ehea_update_bcmc_registrations())
> > rather than at each callsite.
> >
> > Signed-off-by: Sebastien Dugue <sebastien.dugue@xxxxxxxx>
> > ---
> > drivers/net/ehea/ehea_main.c | 26 ++++----------------------
> > 1 files changed, 4 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/net/ehea/ehea_main.c b/drivers/net/ehea/ehea_main.c
> > index b70c531..c765ec6 100644
> > --- a/drivers/net/ehea/ehea_main.c
> > +++ b/drivers/net/ehea/ehea_main.c
> > @@ -219,9 +219,11 @@ static void ehea_update_firmware_handles(void)
> > }
> >
> > out_update:
> > + mutex_lock(&ehea_fw_handles.lock);
> > kfree(ehea_fw_handles.arr);
> > ehea_fw_handles.arr = arr;
> > ehea_fw_handles.num_entries = i;
> > + mutex_unlock(&ehea_fw_handles.lock);
> > }
> >
> > static void ehea_update_bcmc_registrations(void)
> > @@ -293,9 +295,11 @@ static void ehea_update_bcmc_registrations(void)
> > }
> >
> > out_update:
> > + spin_lock(&ehea_bcmc_regs.lock);
> > kfree(ehea_bcmc_regs.arr);
> > ehea_bcmc_regs.arr = arr;
> > ehea_bcmc_regs.num_entries = i;
> > + spin_unlock(&ehea_bcmc_regs.lock);
> > }
> >
> > static struct net_device_stats *ehea_get_stats(struct net_device *dev)
> > @@ -1770,8 +1774,6 @@ static int ehea_set_mac_addr(struct net_device *dev, void *sa)
> >
> > memcpy(dev->dev_addr, mac_addr->sa_data, dev->addr_len);
> >
> > - spin_lock(&ehea_bcmc_regs.lock);
> > -
> > /* Deregister old MAC in pHYP */
> > if (port->state == EHEA_PORT_UP) {
> > ret = ehea_broadcast_reg_helper(port, H_DEREG_BCMC);
> > @@ -1792,7 +1794,6 @@ static int ehea_set_mac_addr(struct net_device *dev, void *sa)
> >
> > out_upregs:
> > ehea_update_bcmc_registrations();
> > - spin_unlock(&ehea_bcmc_regs.lock);
> > out_free:
> > kfree(cb0);
> > out:
> > @@ -1954,8 +1955,6 @@ static void ehea_set_multicast_list(struct net_device *dev)
> > }
> > ehea_promiscuous(dev, 0);
> >
> > - spin_lock(&ehea_bcmc_regs.lock);
> > -
> > if (dev->flags & IFF_ALLMULTI) {
> > ehea_allmulti(dev, 1);
> > goto out;
> > @@ -1985,7 +1984,6 @@ static void ehea_set_multicast_list(struct net_device *dev)
> > }
> > out:
> > ehea_update_bcmc_registrations();
> > - spin_unlock(&ehea_bcmc_regs.lock);
> > return;
> > }
> >
> > @@ -2466,8 +2464,6 @@ static int ehea_up(struct net_device *dev)
> > if (port->state == EHEA_PORT_UP)
> > return 0;
> >
> > - mutex_lock(&ehea_fw_handles.lock);
> > -
> > ret = ehea_port_res_setup(port, port->num_def_qps,
> > port->num_add_tx_qps);
> > if (ret) {
> > @@ -2504,8 +2500,6 @@ static int ehea_up(struct net_device *dev)
> > }
> > }
> >
> > - spin_lock(&ehea_bcmc_regs.lock);
> > -
> > ret = ehea_broadcast_reg_helper(port, H_REG_BCMC);
> > if (ret) {
> > ret = -EIO;
> > @@ -2527,10 +2521,8 @@ out:
> > ehea_info("Failed starting %s. ret=%i", dev->name, ret);
> >
> > ehea_update_bcmc_registrations();
> > - spin_unlock(&ehea_bcmc_regs.lock);
> >
> > ehea_update_firmware_handles();
> > - mutex_unlock(&ehea_fw_handles.lock);
> >
> > return ret;
> > }
> > @@ -2580,9 +2572,6 @@ static int ehea_down(struct net_device *dev)
> > if (port->state == EHEA_PORT_DOWN)
> > return 0;
> >
> > - mutex_lock(&ehea_fw_handles.lock);
> > -
> > - spin_lock(&ehea_bcmc_regs.lock);
> > ehea_drop_multicast_list(dev);
> > ehea_broadcast_reg_helper(port, H_DEREG_BCMC);
> >
> > @@ -2591,7 +2580,6 @@ static int ehea_down(struct net_device *dev)
> > port->state = EHEA_PORT_DOWN;
> >
> > ehea_update_bcmc_registrations();
> > - spin_unlock(&ehea_bcmc_regs.lock);
> >
> > ret = ehea_clean_all_portres(port);
> > if (ret)
> > @@ -2599,7 +2587,6 @@ static int ehea_down(struct net_device *dev)
> > dev->name, ret);
> >
> > ehea_update_firmware_handles();
> > - mutex_unlock(&ehea_fw_handles.lock);
> >
> > return ret;
> > }
> > @@ -3378,7 +3365,6 @@ static int __devinit ehea_probe_adapter(struct of_device *dev,
> > ehea_error("Invalid ibmebus device probed");
> > return -EINVAL;
> > }
> > - mutex_lock(&ehea_fw_handles.lock);
> >
> > adapter = kzalloc(sizeof(*adapter), GFP_KERNEL);
> > if (!adapter) {
> > @@ -3462,7 +3448,6 @@ out_free_ad:
> >
> > out:
> > ehea_update_firmware_handles();
> > - mutex_unlock(&ehea_fw_handles.lock);
> > return ret;
> > }
> >
> > @@ -3481,8 +3466,6 @@ static int __devexit ehea_remove(struct of_device *dev)
> >
> > flush_scheduled_work();
> >
> > - mutex_lock(&ehea_fw_handles.lock);
> > -
> > ibmebus_free_irq(adapter->neq->attr.ist1, adapter);
> > tasklet_kill(&adapter->neq_tasklet);
> >
> > @@ -3492,7 +3475,6 @@ static int __devexit ehea_remove(struct of_device *dev)
> > kfree(adapter);
> >
> > ehea_update_firmware_handles();
> > - mutex_unlock(&ehea_fw_handles.lock);
> >
> > return 0;
> > }
>
>
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Next message: Dave Chinner: "Re: 2.6.27-rc6: lockdep warning: iprune_mutex atshrink_icache_memory+0x38/0x1a8"
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Next in thread: Thomas Klein: "Re: [PATCH 2/2] ehea: fix mutex and spinlock use"
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