Commit 25c411fc authored by John Stultz's avatar John Stultz Committed by Peter Zijlstra
Browse files

sched: Add CONFIG_SCHED_PROXY_EXEC & boot argument to enable/disable 



Add a CONFIG_SCHED_PROXY_EXEC option, along with a boot argument
sched_proxy_exec= that can be used to disable the feature at boot
time if CONFIG_SCHED_PROXY_EXEC was enabled.

Also uses this option to allow the rq->donor to be different from
rq->curr.

Signed-off-by: default avatarJohn Stultz <jstultz@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarK Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lkml.kernel.org/r/20250712033407.2383110-2-jstultz@google.com
parent 8f214615

Documentation/admin-guide/kernel-parameters.txt

+5 −0
Original line number Diff line number Diff line
@@ -6387,6 +6387,11 @@ 
	sa1100ir	[NET]

			See drivers/net/irda/sa1100_ir.c.



	sched_proxy_exec= [KNL]

			Enables or disables "proxy execution" style

			solution to mutex-based priority inversion.

			Format: <bool>



	sched_verbose	[KNL,EARLY] Enables verbose scheduler debug messages.



	schedstats=	[KNL,X86] Enable or disable scheduled statistics.

include/linux/sched.h

+13 −0
Original line number Diff line number Diff line
@@ -1656,6 +1656,19 @@ struct task_struct { 
	randomized_struct_fields_end

} __attribute__ ((aligned (64)));



#ifdef CONFIG_SCHED_PROXY_EXEC

DECLARE_STATIC_KEY_TRUE(__sched_proxy_exec);

static inline bool sched_proxy_exec(void)

{

	return static_branch_likely(&__sched_proxy_exec);

}

#else

static inline bool sched_proxy_exec(void)

{

	return false;

}

#endif



#define TASK_REPORT_IDLE	(TASK_REPORT + 1)

#define TASK_REPORT_MAX		(TASK_REPORT_IDLE << 1)

init/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -878,6 +878,18 @@ config UCLAMP_BUCKETS_COUNT 


	  If in doubt, use the default value.



config SCHED_PROXY_EXEC

	bool "Proxy Execution"

	# Avoid some build failures w/ PREEMPT_RT until it can be fixed

	depends on !PREEMPT_RT

	# Need to investigate how to inform sched_ext of split contexts

	depends on !SCHED_CLASS_EXT

	# Not particularly useful until we get to multi-rq proxying

	depends on EXPERT

	help

	  This option enables proxy execution, a mechanism for mutex-owning

	  tasks to inherit the scheduling context of higher priority waiters.



endmenu



#

kernel/sched/core.c

+29 −0
Original line number Diff line number Diff line
@@ -119,6 +119,35 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp); 


DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);



#ifdef CONFIG_SCHED_PROXY_EXEC

DEFINE_STATIC_KEY_TRUE(__sched_proxy_exec);

static int __init setup_proxy_exec(char *str)

{

	bool proxy_enable = true;



	if (*str && kstrtobool(str + 1, &proxy_enable)) {

		pr_warn("Unable to parse sched_proxy_exec=\n");

		return 0;

	}



	if (proxy_enable) {

		pr_info("sched_proxy_exec enabled via boot arg\n");

		static_branch_enable(&__sched_proxy_exec);

	} else {

		pr_info("sched_proxy_exec disabled via boot arg\n");

		static_branch_disable(&__sched_proxy_exec);

	}

	return 1;

}

#else

static int __init setup_proxy_exec(char *str)

{

	pr_warn("CONFIG_SCHED_PROXY_EXEC=n, so it cannot be enabled or disabled at boot time\n");

	return 0;

}

#endif

__setup("sched_proxy_exec", setup_proxy_exec);



/*

 * Debugging: various feature bits

 *

kernel/sched/sched.h

+12 −0
Original line number Diff line number Diff line
@@ -1142,10 +1142,15 @@ struct rq { 
	 */

	unsigned long 		nr_uninterruptible;



#ifdef CONFIG_SCHED_PROXY_EXEC

	struct task_struct __rcu	*donor;  /* Scheduling context */

	struct task_struct __rcu	*curr;   /* Execution context */

#else

	union {

		struct task_struct __rcu *donor; /* Scheduler context */

		struct task_struct __rcu *curr;  /* Execution context */

	};

#endif

	struct sched_dl_entity	*dl_server;

	struct task_struct	*idle;

	struct task_struct	*stop;
@@ -1326,10 +1331,17 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); 
#define cpu_curr(cpu)		(cpu_rq(cpu)->curr)

#define raw_rq()		raw_cpu_ptr(&runqueues)



#ifdef CONFIG_SCHED_PROXY_EXEC

static inline void rq_set_donor(struct rq *rq, struct task_struct *t)

{

	rcu_assign_pointer(rq->donor, t);

}

#else

static inline void rq_set_donor(struct rq *rq, struct task_struct *t)

{

	/* Do nothing */

}

#endif



#ifdef CONFIG_SCHED_CORE

static inline struct cpumask *sched_group_span(struct sched_group *sg);