From 0bed698a334766ed07bacd6cb33f0228003a7f61 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 5 Sep 2013 16:14:00 +0200 Subject: [PATCH] irq: Justify the various softirq stack choices For clarity, comment the various stack choices for softirqs processing, whether we execute them from ksoftirqd or local_irq_enable() calls. Their use on irq_exit() is already commented. Acked-by: Linus Torvalds Signed-off-by: Frederic Weisbecker Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Paul Mackerras Cc: James Hogan Cc: James E.J. Bottomley Cc: Helge Deller Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: David S. Miller Cc: Andrew Morton --- kernel/softirq.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/softirq.c b/kernel/softirq.c index 9f8092b82a94..2b4328ea769f 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -170,8 +170,13 @@ static inline void _local_bh_enable_ip(unsigned long ip) */ sub_preempt_count(SOFTIRQ_DISABLE_OFFSET - 1); - if (unlikely(!in_interrupt() && local_softirq_pending())) + if (unlikely(!in_interrupt() && local_softirq_pending())) { + /* + * Run softirq if any pending. And do it in its own stack + * as we may be calling this deep in a task call stack already. + */ do_softirq(); + } dec_preempt_count(); #ifdef CONFIG_TRACE_IRQFLAGS @@ -769,6 +774,10 @@ static void run_ksoftirqd(unsigned int cpu) { local_irq_disable(); if (local_softirq_pending()) { + /* + * We can safely run softirq on inline stack, as we are not deep + * in the task stack here. + */ __do_softirq(); rcu_note_context_switch(cpu); local_irq_enable(); -- 2.20.1