Messages in this thread Patch in this message | | | From | Al Stone <> | Subject | [PATCH] net: apm: xgene: force XGene enet driver to re-balance IRQ usage | Date | Mon, 17 Sep 2018 17:35:33 -0600 |
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When using the user-space command 'tuned-adm profile network-latency', the XGene enet driver will cause a hang trying to enable IRQs while the system is trying to tune itself to be more responsive to network traffic; dmesg will even tell us that the enables/disables are not in balance. With this fix, we force the driver to only enable_irq() when there has been a previous disable_irq() -- i.e., force the number of calls to each to be balanced. This allows the kernel to continue operating.
In an ideal world, the XGene enet driver would be restructured to avoid this problem (it seems to be an artifact of when additional packets arrive and differences of opinion in how the NIC responds under those circumstances, some of which is controlled by firmware). In the XGene2 driver, this is not an issue.
However, the XGene (aka Mustang) where this NIC is used is most likely at the end of its useful life (APM which originally created the XGene has completely morphed into a new company). It is unlikely the driver restructuring that is needed will ever be done. There are, however, a bunch of these machines out in the real world, and there are many of us still using them daily (me, for example). So, while this patch is not the ideal way to repair the NIC driver, it does work and allows us to continue using these boxes for a while longer.
Cc: Iyappan Subramanian <isubramanian@apm.com> Cc: Keyur Chudgar <kchudgar@apm.com> Cc: Quan Nguyen <qnguyen@apm.com> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: Al Stone <ahs3@redhat.com> --- drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c index 3b889efddf78..90fb87f7e24e 100644 --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c @@ -866,8 +866,11 @@ static int xgene_enet_napi(struct napi_struct *napi, const int budget) processed = xgene_enet_process_ring(ring, budget); if (processed != budget) { + struct irq_desc *desc = irq_to_desc(ring->irq); + napi_complete_done(napi, processed); - enable_irq(ring->irq); + if (desc && desc->depth > 0) + enable_irq(ring->irq); } return processed; -- 2.17.1
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