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| author | Peter Zijlstra <peterz@infradead.org> | 2022-05-17 13:46:54 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-05-19 23:46:13 +0200 |
| commit | 546a3fee174969ff323d70ff27b1ef181f0d7ceb (patch) | |
| tree | 35b15b82da76831919f3d48539f0c7c2b1d3882d /kernel | |
| parent | 734387ec2f9d77b00276042b1fa7c95f48ee879d (diff) | |
| download | linux-546a3fee174969ff323d70ff27b1ef181f0d7ceb.tar.bz2 | |
sched: Reverse sched_class layout
Because GCC-12 is fully stupid about array bounds and it's just really
hard to get a solid array definition from a linker script, flip the
array order to avoid needing negative offsets :-/
This makes the whole relational pointer magic a little less obvious, but
alas.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/YoOLLmLG7HRTXeEm@hirez.programming.kicks-ass.net
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/core.c | 12 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 15 |
2 files changed, 14 insertions, 13 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2c9f5e97682f..66c4e5922fe1 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2193,7 +2193,7 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) { if (p->sched_class == rq->curr->sched_class) rq->curr->sched_class->check_preempt_curr(rq, p, flags); - else if (p->sched_class > rq->curr->sched_class) + else if (sched_class_above(p->sched_class, rq->curr->sched_class)) resched_curr(rq); /* @@ -5692,7 +5692,7 @@ __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) * higher scheduling class, because otherwise those lose the * opportunity to pull in more work from other CPUs. */ - if (likely(prev->sched_class <= &fair_sched_class && + if (likely(!sched_class_above(prev->sched_class, &fair_sched_class) && rq->nr_running == rq->cfs.h_nr_running)) { p = pick_next_task_fair(rq, prev, rf); @@ -9472,11 +9472,11 @@ void __init sched_init(void) int i; /* Make sure the linker didn't screw up */ - BUG_ON(&idle_sched_class + 1 != &fair_sched_class || - &fair_sched_class + 1 != &rt_sched_class || - &rt_sched_class + 1 != &dl_sched_class); + BUG_ON(&idle_sched_class != &fair_sched_class + 1 || + &fair_sched_class != &rt_sched_class + 1 || + &rt_sched_class != &dl_sched_class + 1); #ifdef CONFIG_SMP - BUG_ON(&dl_sched_class + 1 != &stop_sched_class); + BUG_ON(&dl_sched_class != &stop_sched_class + 1); #endif wait_bit_init(); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index fe4d1acb7e38..2ce18584dca3 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2177,6 +2177,8 @@ static inline void set_next_task(struct rq *rq, struct task_struct *next) * * include/asm-generic/vmlinux.lds.h * + * *CAREFUL* they are laid out in *REVERSE* order!!! + * * Also enforce alignment on the instance, not the type, to guarantee layout. */ #define DEFINE_SCHED_CLASS(name) \ @@ -2185,17 +2187,16 @@ const struct sched_class name##_sched_class \ __section("__" #name "_sched_class") /* Defined in include/asm-generic/vmlinux.lds.h */ -extern struct sched_class __begin_sched_classes[]; -extern struct sched_class __end_sched_classes[]; - -#define sched_class_highest (__end_sched_classes - 1) -#define sched_class_lowest (__begin_sched_classes - 1) +extern struct sched_class __sched_class_highest[]; +extern struct sched_class __sched_class_lowest[]; #define for_class_range(class, _from, _to) \ - for (class = (_from); class != (_to); class--) + for (class = (_from); class < (_to); class++) #define for_each_class(class) \ - for_class_range(class, sched_class_highest, sched_class_lowest) + for_class_range(class, __sched_class_highest, __sched_class_lowest) + +#define sched_class_above(_a, _b) ((_a) < (_b)) extern const struct sched_class stop_sched_class; extern const struct sched_class dl_sched_class; |