irq_work: allow certain work in hard irq context

irq_work is processed in softirq context on -RT because we want to avoid
long latencies which might arise from processing lots of perf events.
The noHZ-full mode requires its callback to be called from real hardirq
context (commit 76c24fb ("nohz: New APIs to re-evaluate the tick on full
dynticks CPUs")). If it is called from a thread context we might get
wrong results for checks like "is_idle_task(current)".
This patch introduces a second list (hirq_work_list) which will be used
if irq_work_run() has been invoked from hardirq context and process only
work items marked with IRQ_WORK_HARD_IRQ.

This patch also removes arch_irq_work_raise() from sparc & powerpc like
it is already done for x86. Atleast for powerpc it is somehow
superfluous because it is called from the timer interrupt which should
invoke update_process_times().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/sparc/kernel/pcr.c b/arch/sparc/kernel/pcr.c
index 7e967c8..927d9c5 100644
--- a/arch/sparc/kernel/pcr.c
+++ b/arch/sparc/kernel/pcr.c
@@ -43,10 +43,12 @@ void __irq_entry deferred_pcr_work_irq(int irq, struct pt_regs *regs)
 	set_irq_regs(old_regs);
 }
 
+#ifndef CONFIG_PREEMPT_RT_FULL
 void arch_irq_work_raise(void)
 {
 	set_softint(1 << PIL_DEFERRED_PCR_WORK);
 }
+#endif
 
 const struct pcr_ops *pcr_ops;
 EXPORT_SYMBOL_GPL(pcr_ops);