Subject: Re: [net-next 16/16] igb: Unset IGB_FLAG_HAS_MSIX-flag when falling back to msi-only

From: Christoph Paasch <[email-masked]>
Date: Sun, 23 Mar 2014 15:32:15 +0100

On 21/03/14 - 12:10:06, Jeff Kirsher wrote:
> From: Christoph Paasch <[email-masked]>
> 
> Prior to cd14ef54d25 (igb: Change to use statically allocated array for
> MSIx entries), having msix_entries different from NULL was an indicator
> that MSIX is enabled.
> In igb_set_interrupt_capabiliy we may fall back to MSI-only. Prior to
> the above patch msix_entries was set to NULL by
> igb_reset_interrupt_capability.
> 
> However, now we are checking the flag for IGB_FLAG_HAS_MSIX and so the
> stack gets completly confused:
> 
> [   42.659791] ------------[ cut here ]------------
> [   42.715032] WARNING: CPU: 7 PID: 0 at net/sched/sch_generic.c:264 dev_watchdog+0x15c/0x1fb()
> [   42.848263] NETDEV WATCHDOG: eth0 (igb): transmit queue 0 timed out
> [   42.923253] Modules linked in:
> [   42.959875] CPU: 7 PID: 0 Comm: swapper/7 Not tainted 3.14.0-rc2-mptcp #437
> [   43.043184] Hardware name: HP ProLiant DL165 G7, BIOS O37 01/26/2011
> [   43.119215]  0000000000000108 ffff88023fdc3da8 ffffffff81487847 0000000000000108
> [   43.208165]  ffff88023fdc3df8 ffff88023fdc3de8 ffffffff81034e7d ffff88023fdc3dd8
> [   43.297120]  ffffffff813fff10 ffff880236018000 ffff880236b178c0 0000000000000008
> [   43.386071] Call Trace:
> [   43.415303]  <IRQ>  [<ffffffff81487847>] dump_stack+0x49/0x62
> [   43.484174]  [<ffffffff81034e7d>] warn_slowpath_common+0x77/0x91
> [   43.556049]  [<ffffffff813fff10>] ? dev_watchdog+0x15c/0x1fb
> [   43.623759]  [<ffffffff81034f2b>] warn_slowpath_fmt+0x41/0x43
> [   43.692511]  [<ffffffff813fff10>] dev_watchdog+0x15c/0x1fb
> [   43.758141]  [<ffffffff813ffdb4>] ? __netdev_watchdog_up+0x64/0x64
> [   43.832091]  [<ffffffff8103cd04>] call_timer_fn+0x17/0x6f
> [   43.896682]  [<ffffffff8103cebe>] run_timer_softirq+0x162/0x1a2
> [   43.967511]  [<ffffffff81038520>] __do_softirq+0xcd/0x1cc
> [   44.032104]  [<ffffffff81038689>] irq_exit+0x3a/0x48
> [   44.091492]  [<ffffffff81026d43>] smp_apic_timer_interrupt+0x43/0x50
> [   44.167525]  [<ffffffff8148c24a>] apic_timer_interrupt+0x6a/0x70
> [   44.239392]  <EOI>  [<ffffffff8100992c>] ? default_idle+0x6/0x8
> [   44.310343]  [<ffffffff81009b31>] arch_cpu_idle+0x13/0x18
> [   44.374934]  [<ffffffff81066126>] cpu_startup_entry+0xa7/0x101
> [   44.444724]  [<ffffffff81025660>] start_secondary+0x1b2/0x1b7
> [   44.513472] ---[ end trace a5a075fd4e7f854f ]---
> [   44.568753] igb 0000:04:00.0 eth0: Reset adapter
> [   46.206945] random: nonblocking pool is initialized
> [   46.465670] irq 44: nobody cared (try booting with the "irqpoll" option)
> [   46.545862] CPU: 7 PID: 0 Comm: swapper/7 Tainted: G        W    3.14.0-rc2-mptcp #437
> [   46.640610] Hardware name: HP ProLiant DL165 G7, BIOS O37 01/26/2011
> [   46.716641]  ffff8802363f8c84 ffff88023fdc3e38 ffffffff81487847 00000000a03cdb6d
> [   46.805598]  ffff8802363f8c00 ffff88023fdc3e68 ffffffff81068489 0000007f81825400
> [   46.894539]  ffff8802363f8c00 0000000000000000 0000000000000000 ffff88023fdc3ea8
> [   46.983484] Call Trace:
> [   47.012714]  <IRQ>  [<ffffffff81487847>] dump_stack+0x49/0x62
> [   47.081585]  [<ffffffff81068489>] __report_bad_irq+0x35/0xc1
> [   47.149295]  [<ffffffff81068683>] note_interrupt+0x16e/0x1ea
> [   47.217006]  [<ffffffff8106679e>] handle_irq_event_percpu+0x116/0x12e
> [   47.294075]  [<ffffffff810667e9>] handle_irq_event+0x33/0x4f
> [   47.361787]  [<ffffffff81068c95>] handle_fasteoi_irq+0x83/0xd1
> [   47.431577]  [<ffffffff81003d5b>] handle_irq+0x1f/0x28
> [   47.493047]  [<ffffffff81003567>] do_IRQ+0x4e/0xd4
> [   47.550358]  [<ffffffff8148b06a>] common_interrupt+0x6a/0x6a
> [   47.618066]  <EOI>  [<ffffffff8100992c>] ? default_idle+0x6/0x8
> [   47.689016]  [<ffffffff81009b31>] arch_cpu_idle+0x13/0x18
> [   47.753605]  [<ffffffff81066126>] cpu_startup_entry+0xa7/0x101
> [   47.823397]  [<ffffffff81025660>] start_secondary+0x1b2/0x1b7
> [   47.892146] handlers:
> [   47.919301] [<ffffffff812fbd7d>] igb_intr
> 
> So, this patch unsets the flag to indicate that we are not using MSIX.
> This patch does exactly this: Unsetting the flag when falling back to MSI.
> 
> Fixes: cd14ef54d25b (igb: Change to use statically allocated array for MSIx entries)
> Cc: Carolyn Wyborny <[email-masked]>
> Signed-off-by: Christoph Paasch <[email-masked]>
> Tested-by: Jeff Pieper <[email-masked]>
> Signed-off-by: Jeff Kirsher <[email-masked]>

Same here - cd14ef54d25b is part of 3.14-rc1. I think it should go into net
instead of net-next.

Cheers,
Christoph

> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index 6acf787..cd20409 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -1149,6 +1149,7 @@ static void igb_set_interrupt_capability(struct igb_adapter *adapter, bool msix)
>  
>  	/* If we can't do MSI-X, try MSI */
>  msi_only:
> +	adapter->flags &= ~IGB_FLAG_HAS_MSIX;
>  #ifdef CONFIG_PCI_IOV
>  	/* disable SR-IOV for non MSI-X configurations */
>  	if (adapter->vf_data) {
> -- 
> 1.8.3.1
>