On 1/30/25 20:24, Sebastian Andrzej Siewior wrote:
On 2025-01-06 10:49:19 [+0530], Shrikanth Hegde wrote:
--- a/arch/powerpc/kernel/interrupt.c
Thanks for taking a look.
+
#ifdef CONFIG_PPC_BOOK3S_64
DEFINE_STATIC_KEY_FALSE(interrupt_exit_not_reentrant);
static inline bool exit_must_hard_disable(void)
@@ -396,7 +400,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct
pt_regs *regs)
/* Returning to a kernel context with local irqs enabled. */
WARN_ON_ONCE(!(regs->msr & MSR_EE));
again:
- if (IS_ENABLED(CONFIG_PREEMPTION)) {
+ if (preempt_model_preemptible()) {
CONFIG_HAVE_PREEMPT_DYNAMIC_KEY is the only option, right? Wouldn't
| #DEFINE need_irq_preemption() \
| (static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
|
| if (need_irq_preemption()) {
be a bit smaller/ quicker? This could be a fast path ;)
I am okay with either way. I did try both[1], there wasn't any significant
difference,
hence chose a simpler one. May be system size, workload pattern might matter.
Let me do some more testing to see which one wins.
Is there any specific benchmark which might help here?
[1]:
https://lore.kernel.org/all/b98b7795-070a-4d9c-9599-445c2ff55...@linux.ibm.com/
/* Return to preemptible kernel context */
if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) {
if (preempt_count() == 0)
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index edf5cabe5dfd..2556fa8ec019 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -266,7 +266,11 @@ static int __die(const char *str, struct pt_regs *regs,
long err)
printk("%s PAGE_SIZE=%luK%s%s%s%s%s%s %s\n",
IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN) ? "LE" : "BE",
PAGE_SIZE / 1024, get_mmu_str(),
- IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "",
+ preempt_model_none() ? "none" :
+ preempt_model_voluntary() ? "voluntary" :
+ preempt_model_full() ? "full" :
+ preempt_model_lazy() ? "lazy" :
+ "",
So intend to rework this part. I have patches stashed at
https://git.kernel.org/pub/scm/linux/kernel/git/bigeasy/staging.git/log/?h=preemption_string
which I didn't sent yet due to the merge window. Just a heads up ;)
Makes sense. I had seen at-least two places where this code was there,
ftrace/powerpc.
There were way more places..
You want me to remove this part?
IS_ENABLED(CONFIG_SMP) ? " SMP" : "",
IS_ENABLED(CONFIG_SMP) ? (" NR_CPUS=" __stringify(NR_CPUS)) : "",
debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "",
Sebastian
