From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Kan Liang kan.liang@linux.intel.com
[ Upstream commit a5398bffc01fe044848c5024e5e867e407f239b8 ]
Sometimes the PMU internal buffers have to be flushed for per-CPU events during a context switch, e.g., large PEBS. Otherwise, the perf tool may report samples in locations that do not belong to the process where the samples are processed in, because PEBS does not tag samples with PID/TID.
The current code only flush the buffers for a per-task event. It doesn't check a per-CPU event.
Add a new event state flag, PERF_ATTACH_SCHED_CB, to indicate that the PMU internal buffers have to be flushed for this event during a context switch.
Add sched_cb_entry and perf_sched_cb_usages back to track the PMU/cpuctx which is required to be flushed.
Only need to invoke the sched_task() for per-CPU events in this patch. The per-task events have been handled in perf_event_context_sched_in/out already.
Fixes: 9c964efa4330 ("perf/x86/intel: Drain the PEBS buffer during context switches") Reported-by: Gabriel Marin gmx@google.com Originally-by: Namhyung Kim namhyung@kernel.org Signed-off-by: Kan Liang kan.liang@linux.intel.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lkml.kernel.org/r/20201130193842.10569-1-kan.liang@linux.intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/perf_event.h | 2 ++ kernel/events/core.c | 42 ++++++++++++++++++++++++++++++++++---- 2 files changed, 40 insertions(+), 4 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 9a38f579bc76..419a4d77de00 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -606,6 +606,7 @@ struct swevent_hlist { #define PERF_ATTACH_TASK 0x04 #define PERF_ATTACH_TASK_DATA 0x08 #define PERF_ATTACH_ITRACE 0x10 +#define PERF_ATTACH_SCHED_CB 0x20
struct perf_cgroup; struct perf_buffer; @@ -872,6 +873,7 @@ struct perf_cpu_context { struct list_head cgrp_cpuctx_entry; #endif
+ struct list_head sched_cb_entry; int sched_cb_usage;
int online; diff --git a/kernel/events/core.c b/kernel/events/core.c index 55d18791a72d..8425dbc1d239 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -385,6 +385,7 @@ static DEFINE_MUTEX(perf_sched_mutex); static atomic_t perf_sched_count;
static DEFINE_PER_CPU(atomic_t, perf_cgroup_events); +static DEFINE_PER_CPU(int, perf_sched_cb_usages); static DEFINE_PER_CPU(struct pmu_event_list, pmu_sb_events);
static atomic_t nr_mmap_events __read_mostly; @@ -3474,11 +3475,16 @@ static void perf_event_context_sched_out(struct task_struct *task, int ctxn, } }
+static DEFINE_PER_CPU(struct list_head, sched_cb_list); + void perf_sched_cb_dec(struct pmu *pmu) { struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
- --cpuctx->sched_cb_usage; + this_cpu_dec(perf_sched_cb_usages); + + if (!--cpuctx->sched_cb_usage) + list_del(&cpuctx->sched_cb_entry); }
@@ -3486,7 +3492,10 @@ void perf_sched_cb_inc(struct pmu *pmu) { struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
- cpuctx->sched_cb_usage++; + if (!cpuctx->sched_cb_usage++) + list_add(&cpuctx->sched_cb_entry, this_cpu_ptr(&sched_cb_list)); + + this_cpu_inc(perf_sched_cb_usages); }
/* @@ -3515,6 +3524,24 @@ static void __perf_pmu_sched_task(struct perf_cpu_context *cpuctx, bool sched_in perf_ctx_unlock(cpuctx, cpuctx->task_ctx); }
+static void perf_pmu_sched_task(struct task_struct *prev, + struct task_struct *next, + bool sched_in) +{ + struct perf_cpu_context *cpuctx; + + if (prev == next) + return; + + list_for_each_entry(cpuctx, this_cpu_ptr(&sched_cb_list), sched_cb_entry) { + /* will be handled in perf_event_context_sched_in/out */ + if (cpuctx->task_ctx) + continue; + + __perf_pmu_sched_task(cpuctx, sched_in); + } +} + static void perf_event_switch(struct task_struct *task, struct task_struct *next_prev, bool sched_in);
@@ -3537,6 +3564,9 @@ void __perf_event_task_sched_out(struct task_struct *task, { int ctxn;
+ if (__this_cpu_read(perf_sched_cb_usages)) + perf_pmu_sched_task(task, next, false); + if (atomic_read(&nr_switch_events)) perf_event_switch(task, next, false);
@@ -3845,6 +3875,9 @@ void __perf_event_task_sched_in(struct task_struct *prev,
if (atomic_read(&nr_switch_events)) perf_event_switch(task, prev, true); + + if (__this_cpu_read(perf_sched_cb_usages)) + perf_pmu_sched_task(prev, task, true); }
static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count) @@ -4669,7 +4702,7 @@ static void unaccount_event(struct perf_event *event) if (event->parent) return;
- if (event->attach_state & PERF_ATTACH_TASK) + if (event->attach_state & (PERF_ATTACH_TASK | PERF_ATTACH_SCHED_CB)) dec = true; if (event->attr.mmap || event->attr.mmap_data) atomic_dec(&nr_mmap_events); @@ -11168,7 +11201,7 @@ static void account_event(struct perf_event *event) if (event->parent) return;
- if (event->attach_state & PERF_ATTACH_TASK) + if (event->attach_state & (PERF_ATTACH_TASK | PERF_ATTACH_SCHED_CB)) inc = true; if (event->attr.mmap || event->attr.mmap_data) atomic_inc(&nr_mmap_events); @@ -12960,6 +12993,7 @@ static void __init perf_event_init_all_cpus(void) #ifdef CONFIG_CGROUP_PERF INIT_LIST_HEAD(&per_cpu(cgrp_cpuctx_list, cpu)); #endif + INIT_LIST_HEAD(&per_cpu(sched_cb_list, cpu)); } }