From 99a854d96a633b15db61824dfdd12ee816974c05 Mon Sep 17 00:00:00 2001 From: Darren Hart Date: Tue, 18 May 2010 14:33:07 -0700 Subject: [PATCH] net: ehea: make rx irq handler non-threaded (IRQF_NODELAY) commit 44b341ae13557f646061530d281fbc19c5ae9111 in tip. The underlying hardware is edge triggered but presented by XICS as level triggered. The edge triggered interrupts are not reissued after masking. This is not a problem in mainline which does not mask the interrupt (relying on the EOI mechanism instead). The threaded interrupts in PREEMPT_RT do mask the interrupt, and can lose interrupts that occurred while masked, resulting in a hung ethernet interface. The receive handler simply calls napi_schedule(), as such, there is no significant additional overhead in making this non-threaded, since we either wakeup the threaded irq handler to call napi_schedule(), or just call napi_schedule() directly to wakeup the softirqs. As the receive handler is lockless, there is no need to convert any of the ehea spinlock_t's to raw_spinlock_t's. Without this patch, a simple scp file copy loop would fail quickly (usually seconds). We have over two hours of sustained scp activity with the patch applied. Credit goes to Will Schmidt for lots of instrumentation and tracing which clarified the scenario and to Thomas Gleixner for the incredibly simple solution. Signed-off-by: Darren Hart Acked-by: Will Schmidt Cc: Jan-Bernd Themann Cc: Nivedita Singhvi Cc: Brian King Cc: Michael Ellerman Cc: Doug Maxey LKML-Reference: <4BF30793.5070300@us.ibm.com> Signed-off-by: Thomas Gleixner Signed-off-by: Paul Gortmaker --- drivers/net/ehea/ehea_main.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/ehea/ehea_main.c b/drivers/net/ehea/ehea_main.c index 809ccc9..9239e96 100644 --- a/drivers/net/ehea/ehea_main.c +++ b/drivers/net/ehea/ehea_main.c @@ -1265,8 +1265,8 @@ static int ehea_reg_interrupts(struct net_device *dev) "%s-queue%d", dev->name, i); ret = ibmebus_request_irq(pr->eq->attr.ist1, ehea_recv_irq_handler, - IRQF_DISABLED, pr->int_send_name, - pr); + IRQF_DISABLED | IRQF_NODELAY, + pr->int_send_name, pr); if (ret) { ehea_error("failed registering irq for ehea_queue " "port_res_nr:%d, ist=%X", i, -- 1.7.0.4