From: Anju T Sudhakar anju@linux.vnet.ibm.com
[ Upstream commit a36e8ba60b991d563677227f172db69e030797e6 ]
IMC(In-memory Collection Counters) does performance monitoring in two different modes, i.e accumulation mode(core-imc and thread-imc events), and trace mode(trace-imc events). A cpu thread can either be in accumulation-mode or trace-mode at a time and this is done via the LDBAR register in POWER architecture. The current design does not address the races between thread-imc and trace-imc events.
Patch implements a global id and lock to avoid the races between core, trace and thread imc events. With this global id-lock implementation, the system can either run core, thread or trace imc events at a time. i.e. to run any core-imc events, thread/trace imc events should not be enabled/monitored.
Signed-off-by: Anju T Sudhakar anju@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20200313055238.8656-1-anju@linux.vnet.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/perf/imc-pmu.c | 173 +++++++++++++++++++++++++++++++----- 1 file changed, 149 insertions(+), 24 deletions(-)
diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c index cb50a9e1fd2d7..eb82dda884e51 100644 --- a/arch/powerpc/perf/imc-pmu.c +++ b/arch/powerpc/perf/imc-pmu.c @@ -44,6 +44,16 @@ static DEFINE_PER_CPU(u64 *, trace_imc_mem); static struct imc_pmu_ref *trace_imc_refc; static int trace_imc_mem_size;
+/* + * Global data structure used to avoid races between thread, + * core and trace-imc + */ +static struct imc_pmu_ref imc_global_refc = { + .lock = __MUTEX_INITIALIZER(imc_global_refc.lock), + .id = 0, + .refc = 0, +}; + static struct imc_pmu *imc_event_to_pmu(struct perf_event *event) { return container_of(event->pmu, struct imc_pmu, pmu); @@ -698,6 +708,16 @@ static int ppc_core_imc_cpu_offline(unsigned int cpu) return -EINVAL;
ref->refc = 0; + /* + * Reduce the global reference count, if this is the + * last cpu in this core and core-imc event running + * in this cpu. + */ + mutex_lock(&imc_global_refc.lock); + if (imc_global_refc.id == IMC_DOMAIN_CORE) + imc_global_refc.refc--; + + mutex_unlock(&imc_global_refc.lock); } return 0; } @@ -710,6 +730,23 @@ static int core_imc_pmu_cpumask_init(void) ppc_core_imc_cpu_offline); }
+static void reset_global_refc(struct perf_event *event) +{ + mutex_lock(&imc_global_refc.lock); + imc_global_refc.refc--; + + /* + * If no other thread is running any + * event for this domain(thread/core/trace), + * set the global id to zero. + */ + if (imc_global_refc.refc <= 0) { + imc_global_refc.refc = 0; + imc_global_refc.id = 0; + } + mutex_unlock(&imc_global_refc.lock); +} + static void core_imc_counters_release(struct perf_event *event) { int rc, core_id; @@ -759,6 +796,8 @@ static void core_imc_counters_release(struct perf_event *event) ref->refc = 0; } mutex_unlock(&ref->lock); + + reset_global_refc(event); }
static int core_imc_event_init(struct perf_event *event) @@ -819,6 +858,29 @@ static int core_imc_event_init(struct perf_event *event) ++ref->refc; mutex_unlock(&ref->lock);
+ /* + * Since the system can run either in accumulation or trace-mode + * of IMC at a time, core-imc events are allowed only if no other + * trace/thread imc events are enabled/monitored. + * + * Take the global lock, and check the refc.id + * to know whether any other trace/thread imc + * events are running. + */ + mutex_lock(&imc_global_refc.lock); + if (imc_global_refc.id == 0 || imc_global_refc.id == IMC_DOMAIN_CORE) { + /* + * No other trace/thread imc events are running in + * the system, so set the refc.id to core-imc. + */ + imc_global_refc.id = IMC_DOMAIN_CORE; + imc_global_refc.refc++; + } else { + mutex_unlock(&imc_global_refc.lock); + return -EBUSY; + } + mutex_unlock(&imc_global_refc.lock); + event->hw.event_base = (u64)pcmi->vbase + (config & IMC_EVENT_OFFSET_MASK); event->destroy = core_imc_counters_release; return 0; @@ -877,7 +939,23 @@ static int ppc_thread_imc_cpu_online(unsigned int cpu)
static int ppc_thread_imc_cpu_offline(unsigned int cpu) { - mtspr(SPRN_LDBAR, 0); + /* + * Set the bit 0 of LDBAR to zero. + * + * If bit 0 of LDBAR is unset, it will stop posting + * the counter data to memory. + * For thread-imc, bit 0 of LDBAR will be set to 1 in the + * event_add function. So reset this bit here, to stop the updates + * to memory in the cpu_offline path. + */ + mtspr(SPRN_LDBAR, (mfspr(SPRN_LDBAR) & (~(1UL << 63)))); + + /* Reduce the refc if thread-imc event running on this cpu */ + mutex_lock(&imc_global_refc.lock); + if (imc_global_refc.id == IMC_DOMAIN_THREAD) + imc_global_refc.refc--; + mutex_unlock(&imc_global_refc.lock); + return 0; }
@@ -916,7 +994,22 @@ static int thread_imc_event_init(struct perf_event *event) if (!target) return -EINVAL;
+ mutex_lock(&imc_global_refc.lock); + /* + * Check if any other trace/core imc events are running in the + * system, if not set the global id to thread-imc. + */ + if (imc_global_refc.id == 0 || imc_global_refc.id == IMC_DOMAIN_THREAD) { + imc_global_refc.id = IMC_DOMAIN_THREAD; + imc_global_refc.refc++; + } else { + mutex_unlock(&imc_global_refc.lock); + return -EBUSY; + } + mutex_unlock(&imc_global_refc.lock); + event->pmu->task_ctx_nr = perf_sw_context; + event->destroy = reset_global_refc; return 0; }
@@ -1063,10 +1156,12 @@ static void thread_imc_event_del(struct perf_event *event, int flags) int core_id; struct imc_pmu_ref *ref;
- mtspr(SPRN_LDBAR, 0); - core_id = smp_processor_id() / threads_per_core; ref = &core_imc_refc[core_id]; + if (!ref) { + pr_debug("imc: Failed to get event reference count\n"); + return; + }
mutex_lock(&ref->lock); ref->refc--; @@ -1082,6 +1177,10 @@ static void thread_imc_event_del(struct perf_event *event, int flags) ref->refc = 0; } mutex_unlock(&ref->lock); + + /* Set bit 0 of LDBAR to zero, to stop posting updates to memory */ + mtspr(SPRN_LDBAR, (mfspr(SPRN_LDBAR) & (~(1UL << 63)))); + /* * Take a snapshot and calculate the delta and update * the event counter values. @@ -1133,7 +1232,18 @@ static int ppc_trace_imc_cpu_online(unsigned int cpu)
static int ppc_trace_imc_cpu_offline(unsigned int cpu) { - mtspr(SPRN_LDBAR, 0); + /* + * No need to set bit 0 of LDBAR to zero, as + * it is set to zero for imc trace-mode + * + * Reduce the refc if any trace-imc event running + * on this cpu. + */ + mutex_lock(&imc_global_refc.lock); + if (imc_global_refc.id == IMC_DOMAIN_TRACE) + imc_global_refc.refc--; + mutex_unlock(&imc_global_refc.lock); + return 0; }
@@ -1226,15 +1336,14 @@ static int trace_imc_event_add(struct perf_event *event, int flags) local_mem = get_trace_imc_event_base_addr(); ldbar_value = ((u64)local_mem & THREAD_IMC_LDBAR_MASK) | TRACE_IMC_ENABLE;
- if (core_imc_refc) - ref = &core_imc_refc[core_id]; + /* trace-imc reference count */ + if (trace_imc_refc) + ref = &trace_imc_refc[core_id]; if (!ref) { - /* If core-imc is not enabled, use trace-imc reference count */ - if (trace_imc_refc) - ref = &trace_imc_refc[core_id]; - if (!ref) - return -EINVAL; + pr_debug("imc: Failed to get the event reference count\n"); + return -EINVAL; } + mtspr(SPRN_LDBAR, ldbar_value); mutex_lock(&ref->lock); if (ref->refc == 0) { @@ -1242,13 +1351,11 @@ static int trace_imc_event_add(struct perf_event *event, int flags) get_hard_smp_processor_id(smp_processor_id()))) { mutex_unlock(&ref->lock); pr_err("trace-imc: Unable to start the counters for core %d\n", core_id); - mtspr(SPRN_LDBAR, 0); return -EINVAL; } } ++ref->refc; mutex_unlock(&ref->lock); - return 0; }
@@ -1274,16 +1381,13 @@ static void trace_imc_event_del(struct perf_event *event, int flags) int core_id = smp_processor_id() / threads_per_core; struct imc_pmu_ref *ref = NULL;
- if (core_imc_refc) - ref = &core_imc_refc[core_id]; + if (trace_imc_refc) + ref = &trace_imc_refc[core_id]; if (!ref) { - /* If core-imc is not enabled, use trace-imc reference count */ - if (trace_imc_refc) - ref = &trace_imc_refc[core_id]; - if (!ref) - return; + pr_debug("imc: Failed to get event reference count\n"); + return; } - mtspr(SPRN_LDBAR, 0); + mutex_lock(&ref->lock); ref->refc--; if (ref->refc == 0) { @@ -1297,6 +1401,7 @@ static void trace_imc_event_del(struct perf_event *event, int flags) ref->refc = 0; } mutex_unlock(&ref->lock); + trace_imc_event_stop(event, flags); }
@@ -1314,10 +1419,30 @@ static int trace_imc_event_init(struct perf_event *event) if (event->attr.sample_period == 0) return -ENOENT;
+ /* + * Take the global lock, and make sure + * no other thread is running any core/thread imc + * events + */ + mutex_lock(&imc_global_refc.lock); + if (imc_global_refc.id == 0 || imc_global_refc.id == IMC_DOMAIN_TRACE) { + /* + * No core/thread imc events are running in the + * system, so set the refc.id to trace-imc. + */ + imc_global_refc.id = IMC_DOMAIN_TRACE; + imc_global_refc.refc++; + } else { + mutex_unlock(&imc_global_refc.lock); + return -EBUSY; + } + mutex_unlock(&imc_global_refc.lock); + event->hw.idx = -1; target = event->hw.target;
event->pmu->task_ctx_nr = perf_hw_context; + event->destroy = reset_global_refc; return 0; }
@@ -1429,10 +1554,10 @@ static void cleanup_all_core_imc_memory(void) static void thread_imc_ldbar_disable(void *dummy) { /* - * By Zeroing LDBAR, we disable thread-imc - * updates. + * By setting 0th bit of LDBAR to zero, we disable thread-imc + * updates to memory. */ - mtspr(SPRN_LDBAR, 0); + mtspr(SPRN_LDBAR, (mfspr(SPRN_LDBAR) & (~(1UL << 63)))); }
void thread_imc_disable(void)