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McKenney" , Metin Kaya , Xuewen Yan , Thomas Gleixner , Daniel Lezcano , Suleiman Souhlal , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a CONFIG_SCHED_PROXY_EXEC option, along with a boot argument sched_proxy_exec=3D 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. Tested-by: K Prateek Nayak Signed-off-by: John Stultz --- v7: * Switch to CONFIG_SCHED_PROXY_EXEC/sched_proxy_exec=3D as suggested by Metin Kaya. * Switch boot arg from =3Ddisable/enable to use kstrtobool(), which supports =3Dyes|no|1|0|true|false|on|off, as also suggested by Metin Kaya, and print a message when a boot argument is used. v8: * Move CONFIG_SCHED_PROXY_EXEC under Scheduler Features as Suggested by Metin * Minor rework reordering with split sched contexts patch v12: * Rework for selected -> donor renaming v14: * Depend on !PREEMPT_RT to avoid build issues for now v15: * Depend on EXPERT while patch series upstreaming is in progress. v16: * Allow "sched_proxy_exec" without "=3Dtrue" to enable proxy-execution at boot time, in addition to the "sched_proxy_exec=3Dtrue" or "sched_proxy_exec=3Dfalse" options as suggested by Steven * Drop the "default n" in Kconfig as suggested by Steven * Add !SCHED_CLASS_EXT dependency until I can investigate if sched_ext can understand split contexts, as suggested by Peter v17: * Expanded the commit message a bit to clarify that the option allows the split contexts (rq->donor and rq->curr) to be different tasks, from feedback from Juri Lelli Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Mel Gorman Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: Daniel Lezcano Cc: Suleiman Souhlal Cc: kernel-team@android.com --- .../admin-guide/kernel-parameters.txt | 5 ++++ include/linux/sched.h | 13 +++++++++ init/Kconfig | 12 ++++++++ kernel/sched/core.c | 29 +++++++++++++++++++ kernel/sched/sched.h | 12 ++++++++ 5 files changed, 71 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index d9fd26b95b340..1ee1e0f628bef 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6304,6 +6304,11 @@ sa1100ir [NET] See drivers/net/irda/sa1100_ir.c. =20 + sched_proxy_exec=3D [KNL] + Enables or disables "proxy execution" style + solution to mutex-based priority inversion. + Format: + sched_verbose [KNL,EARLY] Enables verbose scheduler debug messages. =20 schedstats=3D [KNL,X86] Enable or disable scheduled statistics. diff --git a/include/linux/sched.h b/include/linux/sched.h index f96ac19828934..3cdd598aaa9aa 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1663,6 +1663,19 @@ struct task_struct { */ }; =20 +#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) =20 diff --git a/init/Kconfig b/init/Kconfig index 4cdd1049283c1..168108ea5c82b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -886,6 +886,18 @@ config UCLAMP_BUCKETS_COUNT =20 If in doubt, use the default value. =20 +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 =20 # diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c81cf642dba05..82817650a635b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -118,6 +118,35 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp); =20 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); =20 +#ifdef CONFIG_SCHED_PROXY_EXEC +DEFINE_STATIC_KEY_TRUE(__sched_proxy_exec); +static int __init setup_proxy_exec(char *str) +{ + bool proxy_enable =3D true; + + if (*str && kstrtobool(str + 1, &proxy_enable)) { + pr_warn("Unable to parse sched_proxy_exec=3D\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=3Dn, 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 * diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 47972f34ea701..154f0aa0c6322 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1149,10 +1149,15 @@ struct rq { */ unsigned int nr_uninterruptible; =20 +#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; @@ -1347,10 +1352,17 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues= ); #define cpu_curr(cpu) (cpu_rq(cpu)->curr) #define raw_rq() raw_cpu_ptr(&runqueues) =20 +#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 =20 #ifdef CONFIG_SCHED_CORE static inline struct cpumask *sched_group_span(struct sched_group *sg); --=20 2.49.0.1204.g71687c7c1d-goog