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

From: Sebastien Dugue <[email-masked]>
Date: Tue, 16 Sep 2008 08:57:46 +0200

On Mon, 15 Sep 2008 17:18:27 +0200 Thomas Klein <[email-masked]> 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 <[email-masked]>
> > ---
> >  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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