Avoiding an infinite loop in e1000 82575

[Karim Fodil-Lemelin]

Hi,

I have encountered a strange issue were the igb driver goes into an 
infinite loop (I'm using version - 2.3.10) if many incantations of 
ifconfig are running in a while loop very fast. The following patch 
fixed it for me:

@@ -1052,12 +1052,11 @@ static void e1000_release_swfw_sync_82575(struct 
e1000_hw *hw, u16 mask)
  {
         u32 swfw_sync;

         DEBUGFUNC("e1000_release_swfw_sync_82575");

-       while (e1000_get_hw_semaphore_generic(hw) != E1000_SUCCESS)
-               ; /* Empty */
+       e1000_get_hw_semaphore_generic(hw);

         swfw_sync = E1000_READ_REG(hw, E1000_SW_FW_SYNC);
         swfw_sync &= ~mask;
         E1000_WRITE_REG(hw, E1000_SW_FW_SYNC, swfw_sync);

Now, I haven't seen any side effect of this change except that it fixed 
my issue although I wonder what they are and what effect will this 
change have on the system?

Thanks,

Karim.

PS: Some more information on the devices:

dmesg:

igb0: <Intel(R) PRO/1000 Network Connection version - 2.3.10> port 
0xc880-0xc89f mem 0xfba80000-0xfbafffff,0xfbb78000-0xfbb7bfff irq 16 at 
device 0.0 on pci4
igb0: Using MSIX interrupts with 2 vectors
igb0: Ethernet address: 00:90:0b:2f:b8:00
igb0: [ITHREAD]
igb0: [ITHREAD]
igb1: <Intel(R) PRO/1000 Network Connection version - 2.3.10> port 
0xcc00-0xcc1f mem 0xfbb80000-0xfbbfffff,0xfbb7c000-0xfbb7ffff irq 17 at 
device 0.1 on pci4
igb1: Using MSIX interrupts with 2 vectors
igb1: Ethernet address: 00:90:0b:2f:b8:01
igb1: [ITHREAD]
igb1: [ITHREAD]
igb2: <Intel(R) PRO/1000 Network Connection version - 2.3.10> port 
0xd880-0xd89f mem 0xfbc80000-0xfbcfffff,0xfbd78000-0xfbd7bfff irq 16 at 
device 0.0 on pci5
igb2: Using MSIX interrupts with 2 vectors
igb2: Ethernet address: 00:90:0b:2f:b8:02
igb2: [ITHREAD]
igb2: [ITHREAD]
igb3: <Intel(R) PRO/1000 Network Connection version - 2.3.10> port 
0xdc00-0xdc1f mem 0xfbd80000-0xfbdfffff,0xfbd7c000-0xfbd7ffff irq 17 at 
device 0.1 on pci5
igb3: Using MSIX interrupts with 2 vectors
igb3: Ethernet address: 00:90:0b:2f:b8:03
igb3: [ITHREAD]
igb3: [ITHREAD]

pciconf

igb0 at pci0:4:0:0:        class=0x020000 card=0x00008086 chip=0x150e8086 
rev=0x01 hdr=0x00
igb1 at pci0:4:0:1:        class=0x020000 card=0x00008086 chip=0x150e8086 
rev=0x01 hdr=0x00
igb2 at pci0:5:0:0:        class=0x020000 card=0x00008086 chip=0x150e8086 
rev=0x01 hdr=0x00
igb3 at pci0:5:0:1:        class=0x020000 card=0x00008086 chip=0x150e8086 
rev=0x01 hdr=0x00