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authorLinus Torvalds <torvalds@linux-foundation.org>2021-02-21 12:35:04 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-21 12:35:04 -0800
commit657bd90c93146a929c69cd43addf2804eb70c926 (patch)
treee643825c87070f83df58d37d4daf0417eb17e8c2 /arch/x86/include
parent7b15c27e2f7b6d114770c2922b2c49d2e8f3867c (diff)
parentc5e6fc08feb2b88dc5dac2f3c817e1c2a4cafda4 (diff)
downloadlinux-657bd90c93146a929c69cd43addf2804eb70c926.tar.gz
Merge tag 'sched-core-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar: "Core scheduler updates: - Add CONFIG_PREEMPT_DYNAMIC: this in its current form adds the preempt=none/voluntary/full boot options (default: full), to allow distros to build a PREEMPT kernel but fall back to close to PREEMPT_VOLUNTARY (or PREEMPT_NONE) runtime scheduling behavior via a boot time selection. There's also the /debug/sched_debug switch to do this runtime. This feature is implemented via runtime patching (a new variant of static calls). The scope of the runtime patching can be best reviewed by looking at the sched_dynamic_update() function in kernel/sched/core.c. ( Note that the dynamic none/voluntary mode isn't 100% identical, for example preempt-RCU is available in all cases, plus the preempt count is maintained in all models, which has runtime overhead even with the code patching. ) The PREEMPT_VOLUNTARY/PREEMPT_NONE models, used by the vast majority of distributions, are supposed to be unaffected. - Fix ignored rescheduling after rcu_eqs_enter(). This is a bug that was found via rcutorture triggering a hang. The bug is that rcu_idle_enter() may wake up a NOCB kthread, but this happens after the last generic need_resched() check. Some cpuidle drivers fix it by chance but many others don't. In true 2020 fashion the original bug fix has grown into a 5-patch scheduler/RCU fix series plus another 16 RCU patches to address the underlying issue of missed preemption events. These are the initial fixes that should fix current incarnations of the bug. - Clean up rbtree usage in the scheduler, by providing & using the following consistent set of rbtree APIs: partial-order; less() based: - rb_add(): add a new entry to the rbtree - rb_add_cached(): like rb_add(), but for a rb_root_cached total-order; cmp() based: - rb_find(): find an entry in an rbtree - rb_find_add(): find an entry, and add if not found - rb_find_first(): find the first (leftmost) matching entry - rb_next_match(): continue from rb_find_first() - rb_for_each(): iterate a sub-tree using the previous two - Improve the SMP/NUMA load-balancer: scan for an idle sibling in a single pass. This is a 4-commit series where each commit improves one aspect of the idle sibling scan logic. - Improve the cpufreq cooling driver by getting the effective CPU utilization metrics from the scheduler - Improve the fair scheduler's active load-balancing logic by reducing the number of active LB attempts & lengthen the load-balancing interval. This improves stress-ng mmapfork performance. - Fix CFS's estimated utilization (util_est) calculation bug that can result in too high utilization values Misc updates & fixes: - Fix the HRTICK reprogramming & optimization feature - Fix SCHED_SOFTIRQ raising race & warning in the CPU offlining code - Reduce dl_add_task_root_domain() overhead - Fix uprobes refcount bug - Process pending softirqs in flush_smp_call_function_from_idle() - Clean up task priority related defines, remove *USER_*PRIO and USER_PRIO() - Simplify the sched_init_numa() deduplication sort - Documentation updates - Fix EAS bug in update_misfit_status(), which degraded the quality of energy-balancing - Smaller cleanups" * tag 'sched-core-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (51 commits) sched,x86: Allow !PREEMPT_DYNAMIC entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point entry: Explicitly flush pending rcuog wakeup before last rescheduling point rcu/nocb: Trigger self-IPI on late deferred wake up before user resume rcu/nocb: Perform deferred wake up before last idle's need_resched() check rcu: Pull deferred rcuog wake up to rcu_eqs_enter() callers sched/features: Distinguish between NORMAL and DEADLINE hrtick sched/features: Fix hrtick reprogramming sched/deadline: Reduce rq lock contention in dl_add_task_root_domain() uprobes: (Re)add missing get_uprobe() in __find_uprobe() smp: Process pending softirqs in flush_smp_call_function_from_idle() sched: Harden PREEMPT_DYNAMIC static_call: Allow module use without exposing static_call_key sched: Add /debug/sched_preempt preempt/dynamic: Support dynamic preempt with preempt= boot option preempt/dynamic: Provide irqentry_exit_cond_resched() static call preempt/dynamic: Provide preempt_schedule[_notrace]() static calls preempt/dynamic: Provide cond_resched() and might_resched() static calls preempt: Introduce CONFIG_PREEMPT_DYNAMIC static_call: Provide DEFINE_STATIC_CALL_RET0() ...
Diffstat (limited to 'arch/x86/include')
-rw-r--r--arch/x86/include/asm/preempt.h48
-rw-r--r--arch/x86/include/asm/static_call.h7
2 files changed, 46 insertions, 9 deletions
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 69485ca13665..f8cb8af4de5c 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -5,6 +5,7 @@
#include <asm/rmwcc.h>
#include <asm/percpu.h>
#include <linux/thread_info.h>
+#include <linux/static_call_types.h>
DECLARE_PER_CPU(int, __preempt_count);
@@ -103,16 +104,45 @@ static __always_inline bool should_resched(int preempt_offset)
}
#ifdef CONFIG_PREEMPTION
- extern asmlinkage void preempt_schedule_thunk(void);
-# define __preempt_schedule() \
- asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT)
- extern asmlinkage void preempt_schedule(void);
- extern asmlinkage void preempt_schedule_notrace_thunk(void);
-# define __preempt_schedule_notrace() \
- asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT)
+extern asmlinkage void preempt_schedule(void);
+extern asmlinkage void preempt_schedule_thunk(void);
- extern asmlinkage void preempt_schedule_notrace(void);
-#endif
+#define __preempt_schedule_func preempt_schedule_thunk
+
+extern asmlinkage void preempt_schedule_notrace(void);
+extern asmlinkage void preempt_schedule_notrace_thunk(void);
+
+#define __preempt_schedule_notrace_func preempt_schedule_notrace_thunk
+
+#ifdef CONFIG_PREEMPT_DYNAMIC
+
+DECLARE_STATIC_CALL(preempt_schedule, __preempt_schedule_func);
+
+#define __preempt_schedule() \
+do { \
+ __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule); \
+ asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \
+} while (0)
+
+DECLARE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func);
+
+#define __preempt_schedule_notrace() \
+do { \
+ __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule_notrace); \
+ asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \
+} while (0)
+
+#else /* PREEMPT_DYNAMIC */
+
+#define __preempt_schedule() \
+ asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT);
+
+#define __preempt_schedule_notrace() \
+ asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT);
+
+#endif /* PREEMPT_DYNAMIC */
+
+#endif /* PREEMPTION */
#endif /* __ASM_PREEMPT_H */
diff --git a/arch/x86/include/asm/static_call.h b/arch/x86/include/asm/static_call.h
index c37f11999d0c..cbb67b6030f9 100644
--- a/arch/x86/include/asm/static_call.h
+++ b/arch/x86/include/asm/static_call.h
@@ -37,4 +37,11 @@
#define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) \
__ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; nop; nop; nop; nop")
+
+#define ARCH_ADD_TRAMP_KEY(name) \
+ asm(".pushsection .static_call_tramp_key, \"a\" \n" \
+ ".long " STATIC_CALL_TRAMP_STR(name) " - . \n" \
+ ".long " STATIC_CALL_KEY_STR(name) " - . \n" \
+ ".popsection \n")
+
#endif /* _ASM_STATIC_CALL_H */