diff options
Diffstat (limited to 'debian/patches-rt/0236-sched-Add-support-for-lazy-preemption.patch')
| -rw-r--r-- | debian/patches-rt/0236-sched-Add-support-for-lazy-preemption.patch | 667 |
1 files changed, 667 insertions, 0 deletions
diff --git a/debian/patches-rt/0236-sched-Add-support-for-lazy-preemption.patch b/debian/patches-rt/0236-sched-Add-support-for-lazy-preemption.patch new file mode 100644 index 000000000..0c7ff0691 --- /dev/null +++ b/debian/patches-rt/0236-sched-Add-support-for-lazy-preemption.patch @@ -0,0 +1,667 @@ +From: Thomas Gleixner <tglx@linutronix.de> +Date: Fri, 26 Oct 2012 18:50:54 +0100 +Subject: [PATCH 236/342] sched: Add support for lazy preemption +Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=f58baddb785517ba67a7470fb9278fcf919590ff + +It has become an obsession to mitigate the determinism vs. throughput +loss of RT. Looking at the mainline semantics of preemption points +gives a hint why RT sucks throughput wise for ordinary SCHED_OTHER +tasks. One major issue is the wakeup of tasks which are right away +preempting the waking task while the waking task holds a lock on which +the woken task will block right after having preempted the wakee. In +mainline this is prevented due to the implicit preemption disable of +spin/rw_lock held regions. On RT this is not possible due to the fully +preemptible nature of sleeping spinlocks. + +Though for a SCHED_OTHER task preempting another SCHED_OTHER task this +is really not a correctness issue. RT folks are concerned about +SCHED_FIFO/RR tasks preemption and not about the purely fairness +driven SCHED_OTHER preemption latencies. + +So I introduced a lazy preemption mechanism which only applies to +SCHED_OTHER tasks preempting another SCHED_OTHER task. Aside of the +existing preempt_count each tasks sports now a preempt_lazy_count +which is manipulated on lock acquiry and release. This is slightly +incorrect as for lazyness reasons I coupled this on +migrate_disable/enable so some other mechanisms get the same treatment +(e.g. get_cpu_light). + +Now on the scheduler side instead of setting NEED_RESCHED this sets +NEED_RESCHED_LAZY in case of a SCHED_OTHER/SCHED_OTHER preemption and +therefor allows to exit the waking task the lock held region before +the woken task preempts. That also works better for cross CPU wakeups +as the other side can stay in the adaptive spinning loop. + +For RT class preemption there is no change. This simply sets +NEED_RESCHED and forgoes the lazy preemption counter. + + Initial test do not expose any observable latency increasement, but +history shows that I've been proven wrong before :) + +The lazy preemption mode is per default on, but with +CONFIG_SCHED_DEBUG enabled it can be disabled via: + + # echo NO_PREEMPT_LAZY >/sys/kernel/debug/sched_features + +and reenabled via + + # echo PREEMPT_LAZY >/sys/kernel/debug/sched_features + +The test results so far are very machine and workload dependent, but +there is a clear trend that it enhances the non RT workload +performance. + +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +--- + include/linux/preempt.h | 35 ++++++++++++++- + include/linux/sched.h | 38 +++++++++++++++++ + include/linux/thread_info.h | 12 +++++- + include/linux/trace_events.h | 1 + + kernel/Kconfig.preempt | 6 +++ + kernel/cpu.c | 2 + + kernel/sched/core.c | 83 +++++++++++++++++++++++++++++++++++- + kernel/sched/fair.c | 16 +++---- + kernel/sched/features.h | 3 ++ + kernel/sched/sched.h | 9 ++++ + kernel/trace/trace.c | 36 +++++++++------- + kernel/trace/trace.h | 2 + + kernel/trace/trace_output.c | 14 +++++- + 13 files changed, 228 insertions(+), 29 deletions(-) + +diff --git a/include/linux/preempt.h b/include/linux/preempt.h +index ed8413e7140f..9c74a019bf57 100644 +--- a/include/linux/preempt.h ++++ b/include/linux/preempt.h +@@ -180,6 +180,20 @@ extern void preempt_count_sub(int val); + #define preempt_count_inc() preempt_count_add(1) + #define preempt_count_dec() preempt_count_sub(1) + ++#ifdef CONFIG_PREEMPT_LAZY ++#define add_preempt_lazy_count(val) do { preempt_lazy_count() += (val); } while (0) ++#define sub_preempt_lazy_count(val) do { preempt_lazy_count() -= (val); } while (0) ++#define inc_preempt_lazy_count() add_preempt_lazy_count(1) ++#define dec_preempt_lazy_count() sub_preempt_lazy_count(1) ++#define preempt_lazy_count() (current_thread_info()->preempt_lazy_count) ++#else ++#define add_preempt_lazy_count(val) do { } while (0) ++#define sub_preempt_lazy_count(val) do { } while (0) ++#define inc_preempt_lazy_count() do { } while (0) ++#define dec_preempt_lazy_count() do { } while (0) ++#define preempt_lazy_count() (0) ++#endif ++ + #ifdef CONFIG_PREEMPT_COUNT + + #define preempt_disable() \ +@@ -188,6 +202,12 @@ do { \ + barrier(); \ + } while (0) + ++#define preempt_lazy_disable() \ ++do { \ ++ inc_preempt_lazy_count(); \ ++ barrier(); \ ++} while (0) ++ + #define sched_preempt_enable_no_resched() \ + do { \ + barrier(); \ +@@ -250,6 +270,13 @@ do { \ + __preempt_schedule(); \ + } while (0) + ++#define preempt_lazy_enable() \ ++do { \ ++ dec_preempt_lazy_count(); \ ++ barrier(); \ ++ preempt_check_resched(); \ ++} while (0) ++ + #else /* !CONFIG_PREEMPT */ + #define preempt_enable() \ + do { \ +@@ -257,6 +284,12 @@ do { \ + preempt_count_dec(); \ + } while (0) + ++#define preempt_lazy_enable() \ ++do { \ ++ dec_preempt_lazy_count(); \ ++ barrier(); \ ++} while (0) ++ + #define preempt_enable_notrace() \ + do { \ + barrier(); \ +@@ -323,7 +356,7 @@ do { \ + } while (0) + #define preempt_fold_need_resched() \ + do { \ +- if (tif_need_resched()) \ ++ if (tif_need_resched_now()) \ + set_preempt_need_resched(); \ + } while (0) + +diff --git a/include/linux/sched.h b/include/linux/sched.h +index 7523c0786a63..044bebd3d16f 100644 +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -1733,6 +1733,44 @@ static inline int test_tsk_need_resched(struct task_struct *tsk) + return unlikely(test_tsk_thread_flag(tsk,TIF_NEED_RESCHED)); + } + ++#ifdef CONFIG_PREEMPT_LAZY ++static inline void set_tsk_need_resched_lazy(struct task_struct *tsk) ++{ ++ set_tsk_thread_flag(tsk,TIF_NEED_RESCHED_LAZY); ++} ++ ++static inline void clear_tsk_need_resched_lazy(struct task_struct *tsk) ++{ ++ clear_tsk_thread_flag(tsk,TIF_NEED_RESCHED_LAZY); ++} ++ ++static inline int test_tsk_need_resched_lazy(struct task_struct *tsk) ++{ ++ return unlikely(test_tsk_thread_flag(tsk,TIF_NEED_RESCHED_LAZY)); ++} ++ ++static inline int need_resched_lazy(void) ++{ ++ return test_thread_flag(TIF_NEED_RESCHED_LAZY); ++} ++ ++static inline int need_resched_now(void) ++{ ++ return test_thread_flag(TIF_NEED_RESCHED); ++} ++ ++#else ++static inline void clear_tsk_need_resched_lazy(struct task_struct *tsk) { } ++static inline int need_resched_lazy(void) { return 0; } ++ ++static inline int need_resched_now(void) ++{ ++ return test_thread_flag(TIF_NEED_RESCHED); ++} ++ ++#endif ++ ++ + static inline bool __task_is_stopped_or_traced(struct task_struct *task) + { + if (task->state & (__TASK_STOPPED | __TASK_TRACED)) +diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h +index 62dbecfe9132..57a3d99dc067 100644 +--- a/include/linux/thread_info.h ++++ b/include/linux/thread_info.h +@@ -110,7 +110,17 @@ static inline int test_ti_thread_flag(struct thread_info *ti, int flag) + #define test_thread_flag(flag) \ + test_ti_thread_flag(current_thread_info(), flag) + +-#define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED) ++#ifdef CONFIG_PREEMPT_LAZY ++#define tif_need_resched() (test_thread_flag(TIF_NEED_RESCHED) || \ ++ test_thread_flag(TIF_NEED_RESCHED_LAZY)) ++#define tif_need_resched_now() (test_thread_flag(TIF_NEED_RESCHED)) ++#define tif_need_resched_lazy() test_thread_flag(TIF_NEED_RESCHED_LAZY)) ++ ++#else ++#define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED) ++#define tif_need_resched_now() test_thread_flag(TIF_NEED_RESCHED) ++#define tif_need_resched_lazy() 0 ++#endif + + #ifndef CONFIG_HAVE_ARCH_WITHIN_STACK_FRAMES + static inline int arch_within_stack_frames(const void * const stack, +diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h +index 1cc4d2da954c..72864a11cec0 100644 +--- a/include/linux/trace_events.h ++++ b/include/linux/trace_events.h +@@ -64,6 +64,7 @@ struct trace_entry { + int pid; + unsigned short migrate_disable; + unsigned short padding; ++ unsigned char preempt_lazy_count; + }; + + #define TRACE_EVENT_TYPE_MAX \ +diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt +index 907d72b3ba95..306567f72a3e 100644 +--- a/kernel/Kconfig.preempt ++++ b/kernel/Kconfig.preempt +@@ -6,6 +6,12 @@ config PREEMPT_RT_BASE + bool + select PREEMPT + ++config HAVE_PREEMPT_LAZY ++ bool ++ ++config PREEMPT_LAZY ++ def_bool y if HAVE_PREEMPT_LAZY && PREEMPT_RT_FULL ++ + choice + prompt "Preemption Model" + default PREEMPT_NONE +diff --git a/kernel/cpu.c b/kernel/cpu.c +index 6ae5b18bf3a5..396394ebbc5b 100644 +--- a/kernel/cpu.c ++++ b/kernel/cpu.c +@@ -307,11 +307,13 @@ void pin_current_cpu(void) + return; + } + cpu = smp_processor_id(); ++ preempt_lazy_enable(); + preempt_enable(); + + __read_rt_lock(cpuhp_pin); + + preempt_disable(); ++ preempt_lazy_disable(); + if (cpu != smp_processor_id()) { + __read_rt_unlock(cpuhp_pin); + goto again; +diff --git a/kernel/sched/core.c b/kernel/sched/core.c +index dba425296275..0995748a3a1d 100644 +--- a/kernel/sched/core.c ++++ b/kernel/sched/core.c +@@ -493,6 +493,48 @@ void resched_curr(struct rq *rq) + trace_sched_wake_idle_without_ipi(cpu); + } + ++#ifdef CONFIG_PREEMPT_LAZY ++ ++static int tsk_is_polling(struct task_struct *p) ++{ ++#ifdef TIF_POLLING_NRFLAG ++ return test_tsk_thread_flag(p, TIF_POLLING_NRFLAG); ++#else ++ return 0; ++#endif ++} ++ ++void resched_curr_lazy(struct rq *rq) ++{ ++ struct task_struct *curr = rq->curr; ++ int cpu; ++ ++ if (!sched_feat(PREEMPT_LAZY)) { ++ resched_curr(rq); ++ return; ++ } ++ ++ lockdep_assert_held(&rq->lock); ++ ++ if (test_tsk_need_resched(curr)) ++ return; ++ ++ if (test_tsk_need_resched_lazy(curr)) ++ return; ++ ++ set_tsk_need_resched_lazy(curr); ++ ++ cpu = cpu_of(rq); ++ if (cpu == smp_processor_id()) ++ return; ++ ++ /* NEED_RESCHED_LAZY must be visible before we test polling */ ++ smp_mb(); ++ if (!tsk_is_polling(curr)) ++ smp_send_reschedule(cpu); ++} ++#endif ++ + void resched_cpu(int cpu) + { + struct rq *rq = cpu_rq(cpu); +@@ -2409,6 +2451,9 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) + p->on_cpu = 0; + #endif + init_task_preempt_count(p); ++#ifdef CONFIG_HAVE_PREEMPT_LAZY ++ task_thread_info(p)->preempt_lazy_count = 0; ++#endif + #ifdef CONFIG_SMP + plist_node_init(&p->pushable_tasks, MAX_PRIO); + RB_CLEAR_NODE(&p->pushable_dl_tasks); +@@ -3518,6 +3563,7 @@ static void __sched notrace __schedule(bool preempt) + + next = pick_next_task(rq, prev, &rf); + clear_tsk_need_resched(prev); ++ clear_tsk_need_resched_lazy(prev); + clear_preempt_need_resched(); + + if (likely(prev != next)) { +@@ -3698,6 +3744,30 @@ static void __sched notrace preempt_schedule_common(void) + } while (need_resched()); + } + ++#ifdef CONFIG_PREEMPT_LAZY ++/* ++ * If TIF_NEED_RESCHED is then we allow to be scheduled away since this is ++ * set by a RT task. Oterwise we try to avoid beeing scheduled out as long as ++ * preempt_lazy_count counter >0. ++ */ ++static __always_inline int preemptible_lazy(void) ++{ ++ if (test_thread_flag(TIF_NEED_RESCHED)) ++ return 1; ++ if (current_thread_info()->preempt_lazy_count) ++ return 0; ++ return 1; ++} ++ ++#else ++ ++static inline int preemptible_lazy(void) ++{ ++ return 1; ++} ++ ++#endif ++ + #ifdef CONFIG_PREEMPT + /* + * this is the entry point to schedule() from in-kernel preemption +@@ -3712,7 +3782,8 @@ asmlinkage __visible void __sched notrace preempt_schedule(void) + */ + if (likely(!preemptible())) + return; +- ++ if (!preemptible_lazy()) ++ return; + preempt_schedule_common(); + } + NOKPROBE_SYMBOL(preempt_schedule); +@@ -3739,6 +3810,9 @@ asmlinkage __visible void __sched notrace preempt_schedule_notrace(void) + if (likely(!preemptible())) + return; + ++ if (!preemptible_lazy()) ++ return; ++ + do { + /* + * Because the function tracer can trace preempt_count_sub() +@@ -5505,7 +5579,9 @@ void init_idle(struct task_struct *idle, int cpu) + + /* Set the preempt count _outside_ the spinlocks! */ + init_idle_preempt_count(idle, cpu); +- ++#ifdef CONFIG_HAVE_PREEMPT_LAZY ++ task_thread_info(idle)->preempt_lazy_count = 0; ++#endif + /* + * The idle tasks have their own, simple scheduling class: + */ +@@ -7222,6 +7298,7 @@ void migrate_disable(void) + } + + preempt_disable(); ++ preempt_lazy_disable(); + pin_current_cpu(); + + migrate_disable_update_cpus_allowed(p); +@@ -7289,6 +7366,7 @@ void migrate_enable(void) + arg.dest_cpu = dest_cpu; + + unpin_current_cpu(); ++ preempt_lazy_enable(); + preempt_enable(); + stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); + tlb_migrate_finish(p->mm); +@@ -7297,6 +7375,7 @@ void migrate_enable(void) + } + } + unpin_current_cpu(); ++ preempt_lazy_enable(); + preempt_enable(); + } + EXPORT_SYMBOL(migrate_enable); +diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c +index 16940416d526..d006dfc54a45 100644 +--- a/kernel/sched/fair.c ++++ b/kernel/sched/fair.c +@@ -4104,7 +4104,7 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) + ideal_runtime = sched_slice(cfs_rq, curr); + delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; + if (delta_exec > ideal_runtime) { +- resched_curr(rq_of(cfs_rq)); ++ resched_curr_lazy(rq_of(cfs_rq)); + /* + * The current task ran long enough, ensure it doesn't get + * re-elected due to buddy favours. +@@ -4128,7 +4128,7 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) + return; + + if (delta > ideal_runtime) +- resched_curr(rq_of(cfs_rq)); ++ resched_curr_lazy(rq_of(cfs_rq)); + } + + static void +@@ -4270,7 +4270,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) + * validating it and just reschedule. + */ + if (queued) { +- resched_curr(rq_of(cfs_rq)); ++ resched_curr_lazy(rq_of(cfs_rq)); + return; + } + /* +@@ -4404,7 +4404,7 @@ static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) + * hierarchy can be throttled + */ + if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) +- resched_curr(rq_of(cfs_rq)); ++ resched_curr_lazy(rq_of(cfs_rq)); + } + + static __always_inline +@@ -5112,7 +5112,7 @@ static void hrtick_start_fair(struct rq *rq, struct task_struct *p) + + if (delta < 0) { + if (rq->curr == p) +- resched_curr(rq); ++ resched_curr_lazy(rq); + return; + } + hrtick_start(rq, delta); +@@ -6706,7 +6706,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ + return; + + preempt: +- resched_curr(rq); ++ resched_curr_lazy(rq); + /* + * Only set the backward buddy when the current task is still + * on the rq. This can happen when a wakeup gets interleaved +@@ -9840,7 +9840,7 @@ static void task_fork_fair(struct task_struct *p) + * 'current' within the tree based on its new key value. + */ + swap(curr->vruntime, se->vruntime); +- resched_curr(rq); ++ resched_curr_lazy(rq); + } + + se->vruntime -= cfs_rq->min_vruntime; +@@ -9864,7 +9864,7 @@ prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) + */ + if (rq->curr == p) { + if (p->prio > oldprio) +- resched_curr(rq); ++ resched_curr_lazy(rq); + } else + check_preempt_curr(rq, p, 0); + } +diff --git a/kernel/sched/features.h b/kernel/sched/features.h +index 68de18405857..12a12be6770b 100644 +--- a/kernel/sched/features.h ++++ b/kernel/sched/features.h +@@ -48,6 +48,9 @@ SCHED_FEAT(NONTASK_CAPACITY, true) + + #ifdef CONFIG_PREEMPT_RT_FULL + SCHED_FEAT(TTWU_QUEUE, false) ++# ifdef CONFIG_PREEMPT_LAZY ++SCHED_FEAT(PREEMPT_LAZY, true) ++# endif + #else + + /* +diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h +index 637c408fb2dc..87a05bb90124 100644 +--- a/kernel/sched/sched.h ++++ b/kernel/sched/sched.h +@@ -1643,6 +1643,15 @@ extern void reweight_task(struct task_struct *p, int prio); + extern void resched_curr(struct rq *rq); + extern void resched_cpu(int cpu); + ++#ifdef CONFIG_PREEMPT_LAZY ++extern void resched_curr_lazy(struct rq *rq); ++#else ++static inline void resched_curr_lazy(struct rq *rq) ++{ ++ resched_curr(rq); ++} ++#endif ++ + extern struct rt_bandwidth def_rt_bandwidth; + extern void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime); + +diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c +index 5cb37fa71316..50eee8dcf85c 100644 +--- a/kernel/trace/trace.c ++++ b/kernel/trace/trace.c +@@ -2153,6 +2153,7 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags, + struct task_struct *tsk = current; + + entry->preempt_count = pc & 0xff; ++ entry->preempt_lazy_count = preempt_lazy_count(); + entry->pid = (tsk) ? tsk->pid : 0; + entry->flags = + #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT +@@ -2163,7 +2164,8 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags, + ((pc & NMI_MASK ) ? TRACE_FLAG_NMI : 0) | + ((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) | + ((pc & SOFTIRQ_OFFSET) ? TRACE_FLAG_SOFTIRQ : 0) | +- (tif_need_resched() ? TRACE_FLAG_NEED_RESCHED : 0) | ++ (tif_need_resched_now() ? TRACE_FLAG_NEED_RESCHED : 0) | ++ (need_resched_lazy() ? TRACE_FLAG_NEED_RESCHED_LAZY : 0) | + (test_preempt_need_resched() ? TRACE_FLAG_PREEMPT_RESCHED : 0); + + entry->migrate_disable = (tsk) ? __migrate_disabled(tsk) & 0xFF : 0; +@@ -3364,15 +3366,17 @@ get_total_entries(struct trace_buffer *buf, + + static void print_lat_help_header(struct seq_file *m) + { +- seq_puts(m, "# _------=> CPU# \n" +- "# / _-----=> irqs-off \n" +- "# | / _----=> need-resched \n" +- "# || / _---=> hardirq/softirq \n" +- "# ||| / _--=> preempt-depth \n" +- "# |||| / _--=> migrate-disable\n" +- "# ||||| / delay \n" +- "# cmd pid |||||| time | caller \n" +- "# \\ / ||||| \\ | / \n"); ++ seq_puts(m, "# _--------=> CPU# \n" ++ "# / _-------=> irqs-off \n" ++ "# | / _------=> need-resched \n" ++ "# || / _-----=> need-resched_lazy \n" ++ "# ||| / _----=> hardirq/softirq \n" ++ "# |||| / _---=> preempt-depth \n" ++ "# ||||| / _--=> preempt-lazy-depth\n" ++ "# |||||| / _-=> migrate-disable \n" ++ "# ||||||| / delay \n" ++ "# cmd pid |||||||| time | caller \n" ++ "# \\ / |||||||| \\ | / \n"); + } + + static void print_event_info(struct trace_buffer *buf, struct seq_file *m) +@@ -3410,15 +3414,17 @@ static void print_func_help_header_irq(struct trace_buffer *buf, struct seq_file + tgid ? tgid_space : space); + seq_printf(m, "# %s / _----=> need-resched\n", + tgid ? tgid_space : space); +- seq_printf(m, "# %s| / _---=> hardirq/softirq\n", ++ seq_printf(m, "# %s| / _---=> need-resched_lazy\n", + tgid ? tgid_space : space); +- seq_printf(m, "# %s|| / _--=> preempt-depth\n", ++ seq_printf(m, "# %s|| / _--=> hardirq/softirq\n", + tgid ? tgid_space : space); +- seq_printf(m, "# %s||| / delay\n", ++ seq_printf(m, "# %s||| / preempt-depth\n", + tgid ? tgid_space : space); +- seq_printf(m, "# TASK-PID %sCPU# |||| TIMESTAMP FUNCTION\n", ++ seq_printf(m, "# %s|||| / delay\n", ++ tgid ? tgid_space : space); ++ seq_printf(m, "# TASK-PID %sCPU# ||||| TIMESTAMP FUNCTION\n", + tgid ? " TGID " : space); +- seq_printf(m, "# | | %s | |||| | |\n", ++ seq_printf(m, "# | | %s | ||||| | |\n", + tgid ? " | " : space); + } + +diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h +index 74185fb040f3..7740bcdad355 100644 +--- a/kernel/trace/trace.h ++++ b/kernel/trace/trace.h +@@ -127,6 +127,7 @@ struct kretprobe_trace_entry_head { + * NEED_RESCHED - reschedule is requested + * HARDIRQ - inside an interrupt handler + * SOFTIRQ - inside a softirq handler ++ * NEED_RESCHED_LAZY - lazy reschedule is requested + */ + enum trace_flag_type { + TRACE_FLAG_IRQS_OFF = 0x01, +@@ -136,6 +137,7 @@ enum trace_flag_type { + TRACE_FLAG_SOFTIRQ = 0x10, + TRACE_FLAG_PREEMPT_RESCHED = 0x20, + TRACE_FLAG_NMI = 0x40, ++ TRACE_FLAG_NEED_RESCHED_LAZY = 0x80, + }; + + #define TRACE_BUF_SIZE 1024 +diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c +index 46c96744f09d..3f78b0afb729 100644 +--- a/kernel/trace/trace_output.c ++++ b/kernel/trace/trace_output.c +@@ -448,6 +448,7 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry) + { + char hardsoft_irq; + char need_resched; ++ char need_resched_lazy; + char irqs_off; + int hardirq; + int softirq; +@@ -478,6 +479,9 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry) + break; + } + ++ need_resched_lazy = ++ (entry->flags & TRACE_FLAG_NEED_RESCHED_LAZY) ? 'L' : '.'; ++ + hardsoft_irq = + (nmi && hardirq) ? 'Z' : + nmi ? 'z' : +@@ -486,14 +490,20 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry) + softirq ? 's' : + '.' ; + +- trace_seq_printf(s, "%c%c%c", +- irqs_off, need_resched, hardsoft_irq); ++ trace_seq_printf(s, "%c%c%c%c", ++ irqs_off, need_resched, need_resched_lazy, ++ hardsoft_irq); + + if (entry->preempt_count) + trace_seq_printf(s, "%x", entry->preempt_count); + else + trace_seq_putc(s, '.'); + ++ if (entry->preempt_lazy_count) ++ trace_seq_printf(s, "%x", entry->preempt_lazy_count); ++ else ++ trace_seq_putc(s, '.'); ++ + if (entry->migrate_disable) + trace_seq_printf(s, "%x", entry->migrate_disable); + else |