From c305d524e5dd3c3c7a6035083e30950bea1b52dc Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 2 Feb 2011 17:10:48 +0100 Subject: softirq: Avoid stack switch from ksoftirqd ksoftirqd() calls do_softirq() which switches stacks on several architectures. That makes no sense at all. ksoftirqd's stack is sufficient. Call __do_softirq() directly. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Cc: Benjamin Herrenschmidt Cc: Heiko Carstens Acked-by: David Miller Cc: Paul Mundt Reviewed-by: Frank Rowand LKML-Reference: --- kernel/softirq.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'kernel/softirq.c') diff --git a/kernel/softirq.c b/kernel/softirq.c index 68eb5efec38..c0490464e92 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -738,7 +738,10 @@ static int run_ksoftirqd(void * __bind_cpu) don't process */ if (cpu_is_offline((long)__bind_cpu)) goto wait_to_die; - do_softirq(); + local_irq_disable(); + if (local_softirq_pending()) + __do_softirq(); + local_irq_enable(); preempt_enable_no_resched(); cond_resched(); preempt_disable(); -- cgit v1.2.3-18-g5258 From 8d32a307e4faa8b123dc8a9cd56d1a7525f69ad3 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 23 Feb 2011 23:52:23 +0000 Subject: genirq: Provide forced interrupt threading Add a commandline parameter "threadirqs" which forces all interrupts except those marked IRQF_NO_THREAD to run threaded. That's mostly a debug option to allow retrieving better debug data from crashing interrupt handlers. If "threadirqs" is not enabled on the kernel command line, then there is no impact in the interrupt hotpath. Architecture code needs to select CONFIG_IRQ_FORCED_THREADING after marking the interrupts which cant be threaded IRQF_NO_THREAD. All interrupts which have IRQF_TIMER set are implict marked IRQF_NO_THREAD. Also all PER_CPU interrupts are excluded. Forced threading hard interrupts also forces all soft interrupt handling into thread context. When enabled it might slow down things a bit, but for debugging problems in interrupt code it's a reasonable penalty as it does not immediately crash and burn the machine when an interrupt handler is buggy. Some test results on a Core2Duo machine: Cache cold run of: # time git grep irq_desc non-threaded threaded real 1m18.741s 1m19.061s user 0m1.874s 0m1.757s sys 0m5.843s 0m5.427s # iperf -c server non-threaded [ 3] 0.0-10.0 sec 1.09 GBytes 933 Mbits/sec [ 3] 0.0-10.0 sec 1.09 GBytes 934 Mbits/sec [ 3] 0.0-10.0 sec 1.09 GBytes 933 Mbits/sec threaded [ 3] 0.0-10.0 sec 1.09 GBytes 939 Mbits/sec [ 3] 0.0-10.0 sec 1.09 GBytes 934 Mbits/sec [ 3] 0.0-10.0 sec 1.09 GBytes 937 Mbits/sec Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra LKML-Reference: <20110223234956.772668648@linutronix.de> --- kernel/softirq.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) (limited to 'kernel/softirq.c') diff --git a/kernel/softirq.c b/kernel/softirq.c index c0490464e92..a33fb291124 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -311,9 +311,21 @@ void irq_enter(void) } #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED -# define invoke_softirq() __do_softirq() +static inline void invoke_softirq(void) +{ + if (!force_irqthreads) + __do_softirq(); + else + wakeup_softirqd(); +} #else -# define invoke_softirq() do_softirq() +static inline void invoke_softirq(void) +{ + if (!force_irqthreads) + do_softirq(); + else + wakeup_softirqd(); +} #endif /* -- cgit v1.2.3-18-g5258