From 43c31ac0e665d942fcaba83a725a8b1aeeb7adf0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 21 Oct 2020 15:45:33 +0200 Subject: [PATCH] sched: Remove relyance on STRUCT_ALIGNMENT Florian reported that all of kernel/sched/ is rebuild when CONFIG_BLK_DEV_INITRD is changed, which, while not a bug is unexpected. This is due to us including vmlinux.lds.h. Jakub explained that the problem is that we put the alignment requirement on the type instead of on a variable. Type alignment is a minimum, the compiler is free to pick any larger alignment for a specific instance of the type (eg. the variable). So force the type alignment on all individual variable definitions and remove the undesired dependency on vmlinux.lds.h. Fixes: 85c2ce9104eb ("sched, vmlinux.lds: Increase STRUCT_ALIGNMENT to 64 bytes for GCC-4.9") Reported-by: Florian Fainelli Suggested-by: Jakub Jelinek Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/deadline.c | 4 ++-- kernel/sched/fair.c | 4 ++-- kernel/sched/idle.c | 4 ++-- kernel/sched/rt.c | 4 ++-- kernel/sched/sched.h | 17 +++++++++++++++-- kernel/sched/stop_task.c | 3 +-- 6 files changed, 24 insertions(+), 12 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 0b45dd1..c6ce90f 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2522,8 +2522,8 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p, } } -const struct sched_class dl_sched_class - __section("__dl_sched_class") = { +DEFINE_SCHED_CLASS(dl) = { + .enqueue_task = enqueue_task_dl, .dequeue_task = dequeue_task_dl, .yield_task = yield_task_dl, diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index cd9a37c..f30d35a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -11171,8 +11171,8 @@ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task /* * All the scheduling class methods: */ -const struct sched_class fair_sched_class - __section("__fair_sched_class") = { +DEFINE_SCHED_CLASS(fair) = { + .enqueue_task = enqueue_task_fair, .dequeue_task = dequeue_task_fair, .yield_task = yield_task_fair, diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 846743e..9da69c4 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -458,8 +458,8 @@ static void update_curr_idle(struct rq *rq) /* * Simple, special scheduling class for the per-CPU idle tasks: */ -const struct sched_class idle_sched_class - __section("__idle_sched_class") = { +DEFINE_SCHED_CLASS(idle) = { + /* no enqueue/yield_task for idle tasks */ /* dequeue is not valid, we print a debug message there: */ diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 8a3b1ba..9b27352 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2431,8 +2431,8 @@ static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task) return 0; } -const struct sched_class rt_sched_class - __section("__rt_sched_class") = { +DEFINE_SCHED_CLASS(rt) = { + .enqueue_task = enqueue_task_rt, .dequeue_task = dequeue_task_rt, .yield_task = yield_task_rt, diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 965b296..3e45055 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -67,7 +67,6 @@ #include #include -#include #ifdef CONFIG_PARAVIRT # include @@ -1836,7 +1835,7 @@ struct sched_class { #ifdef CONFIG_FAIR_GROUP_SCHED void (*task_change_group)(struct task_struct *p, int type); #endif -} __aligned(STRUCT_ALIGNMENT); /* STRUCT_ALIGN(), vmlinux.lds.h */ +}; static inline void put_prev_task(struct rq *rq, struct task_struct *prev) { @@ -1850,6 +1849,20 @@ static inline void set_next_task(struct rq *rq, struct task_struct *next) next->sched_class->set_next_task(rq, next, false); } + +/* + * Helper to define a sched_class instance; each one is placed in a separate + * section which is ordered by the linker script: + * + * include/asm-generic/vmlinux.lds.h + * + * Also enforce alignment on the instance, not the type, to guarantee layout. + */ +#define DEFINE_SCHED_CLASS(name) \ +const struct sched_class name##_sched_class \ + __aligned(__alignof__(struct 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[]; diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c index ceb5b6b..91bb10c 100644 --- a/kernel/sched/stop_task.c +++ b/kernel/sched/stop_task.c @@ -109,8 +109,7 @@ static void update_curr_stop(struct rq *rq) /* * Simple, special scheduling class for the per-CPU stop tasks: */ -const struct sched_class stop_sched_class - __section("__stop_sched_class") = { +DEFINE_SCHED_CLASS(stop) = { .enqueue_task = enqueue_task_stop, .dequeue_task = dequeue_task_stop, -- 2.7.4