diff --git a/arch/s390/kernel/perf_cpum_cf.c b/arch/s390/kernel/perf_cpum_cf.c index 2cecc86144e1..1ad3b34be837 100644 --- a/arch/s390/kernel/perf_cpum_cf.c +++ b/arch/s390/kernel/perf_cpum_cf.c @@ -109,6 +109,7 @@ struct cpu_cf_ptr { static struct cpu_cf_root { /* Anchor to per CPU data */ refcount_t refcnt; /* Overall active events */ + unsigned int tskctx; /* Users tracking all CPUs (cpu == -1) */ struct cpu_cf_ptr __percpu *cfptr; } cpu_cf_root; @@ -117,13 +118,15 @@ static struct cpu_cf_root { /* Anchor to per CPU data */ * user space in task context with perf_event_open() and close() * system calls. * - * This mutex serializes functions cpum_cf_alloc_cpu() called at event - * initialization via cpumf_pmu_event_init() and function cpum_cf_free_cpu() - * called at event removal via call back function hw_perf_event_destroy() - * when the event is deleted. They are serialized to enforce correct - * bookkeeping of pointer and reference counts anchored by - * struct cpu_cf_root and the access to cpu_cf_root::refcnt and the - * per CPU pointers stored in cpu_cf_root::cfptr. + * This mutex serializes the allocation and removal of the per CPU counter + * data via cpum_cf_alloc_cpu() and cpum_cf_free_cpu(). They are called with + * this mutex held at event initialization via cpumf_pmu_event_init(), at + * event removal via call back function hw_perf_event_destroy() when the + * event is deleted, and from the CPU hotplug prepare/dead callbacks. The + * mutex enforces correct bookkeeping of pointer and reference counts + * anchored by struct cpu_cf_root and protects the access to + * cpu_cf_root::refcnt, cpu_cf_root::tskctx and the per CPU pointers + * stored in cpu_cf_root::cfptr. */ static DEFINE_MUTEX(pmc_reserve_mutex); @@ -166,12 +169,14 @@ static void cpum_cf_reset_cpu(void *flags) } /* Free per CPU data when the last event is removed. */ -static void cpum_cf_free_root(void) +static void cpum_cf_free_root(unsigned int num) { - if (!refcount_dec_and_test(&cpu_cf_root.refcnt)) + struct cpu_cf_ptr __percpu *p = cpu_cf_root.cfptr; + + if (!refcount_sub_and_test(num, &cpu_cf_root.refcnt)) return; - free_percpu(cpu_cf_root.cfptr); cpu_cf_root.cfptr = NULL; + free_percpu(p); irq_subclass_unregister(IRQ_SUBCLASS_MEASUREMENT_ALERT); on_each_cpu(cpum_cf_reset_cpu, NULL, 1); debug_sprintf_event(cf_dbg, 4, "%s root.refcnt %u cfptr %d\n", @@ -185,17 +190,17 @@ static void cpum_cf_free_root(void) * CPUs possible, which might be larger than the number of CPUs currently * online. */ -static int cpum_cf_alloc_root(void) +static int cpum_cf_alloc_root(unsigned int num) { int rc = 0; - if (refcount_inc_not_zero(&cpu_cf_root.refcnt)) + if (refcount_add_not_zero(num, &cpu_cf_root.refcnt)) return rc; /* The memory is already zeroed. */ cpu_cf_root.cfptr = alloc_percpu(struct cpu_cf_ptr); if (cpu_cf_root.cfptr) { - refcount_set(&cpu_cf_root.refcnt, 1); + refcount_set(&cpu_cf_root.refcnt, num); on_each_cpu(cpum_cf_reset_cpu, NULL, 1); irq_subclass_register(IRQ_SUBCLASS_MEASUREMENT_ALERT); } else { @@ -205,20 +210,23 @@ static int cpum_cf_alloc_root(void) return rc; } -/* Free CPU counter data structure for a PMU */ -static void cpum_cf_free_cpu(int cpu) +/* + * Remove num references to the CPU counter data structure of a PMU. + * Called with pmc_reserve_mutex held. + */ +static void cpum_cf_free_cpu(int cpu, unsigned int num) { struct cpu_cf_events *cpuhw; struct cpu_cf_ptr *p; - mutex_lock(&pmc_reserve_mutex); + lockdep_assert_held(&pmc_reserve_mutex); /* * When invoked via CPU hotplug handler, there might be no events * installed or that particular CPU might not have an * event installed. This anchor pointer can be NULL! */ if (!cpu_cf_root.cfptr) - goto out; + return; p = per_cpu_ptr(cpu_cf_root.cfptr, cpu); cpuhw = p->cpucf; /* @@ -226,28 +234,29 @@ static void cpum_cf_free_cpu(int cpu) * installed on that CPU, but on different CPUs. */ if (!cpuhw) - goto out; + return; - if (refcount_dec_and_test(&cpuhw->refcnt)) { - kfree(cpuhw); + if (refcount_sub_and_test(num, &cpuhw->refcnt)) { p->cpucf = NULL; + kfree(cpuhw); } - cpum_cf_free_root(); -out: - mutex_unlock(&pmc_reserve_mutex); + cpum_cf_free_root(num); } -/* Allocate CPU counter data structure for a PMU. Called under mutex lock. */ -static int cpum_cf_alloc_cpu(int cpu) +/* + * Add num references to the CPU counter data structure of a PMU and + * allocate it when necessary. Called with pmc_reserve_mutex held. + */ +static int cpum_cf_alloc_cpu(int cpu, unsigned int num) { struct cpu_cf_events *cpuhw; struct cpu_cf_ptr *p; int rc; - mutex_lock(&pmc_reserve_mutex); - rc = cpum_cf_alloc_root(); + lockdep_assert_held(&pmc_reserve_mutex); + rc = cpum_cf_alloc_root(num); if (rc) - goto unlock; + return rc; p = per_cpu_ptr(cpu_cf_root.cfptr, cpu); cpuhw = p->cpucf; @@ -255,12 +264,12 @@ static int cpum_cf_alloc_cpu(int cpu) cpuhw = kzalloc_obj(*cpuhw); if (cpuhw) { p->cpucf = cpuhw; - refcount_set(&cpuhw->refcnt, 1); + refcount_set(&cpuhw->refcnt, num); } else { rc = -ENOMEM; } } else { - refcount_inc(&cpuhw->refcnt); + refcount_add(num, &cpuhw->refcnt); } if (rc) { /* @@ -268,10 +277,8 @@ static int cpum_cf_alloc_cpu(int cpu) * cpu_cf_event in not created, its destroy() function is not * invoked. Adjust the reference counter for the anchor. */ - cpum_cf_free_root(); + cpum_cf_free_root(num); } -unlock: - mutex_unlock(&pmc_reserve_mutex); return rc; } @@ -283,39 +290,70 @@ static int cpum_cf_alloc_cpu(int cpu) * perf_event_open() with task context and /dev/hwctr interface. * If cpu is non-zero install event on this CPU only. This setup handles * perf_event_open() with CPU context. + * Users with cpu == -1 are counted in cpu_cf_root::tskctx. The CPU hotplug + * prepare and dead callbacks use this count to install and remove the per + * CPU counter data on a new or dying CPU. */ -static int cpum_cf_alloc(int cpu) +static int cpum_cf_alloc_cpuslocked(int cpu) { cpumask_var_t mask; int rc; + lockdep_assert_cpus_held(); if (cpu == -1) { if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) return -ENOMEM; + mutex_lock(&pmc_reserve_mutex); for_each_online_cpu(cpu) { - rc = cpum_cf_alloc_cpu(cpu); + rc = cpum_cf_alloc_cpu(cpu, 1); if (rc) { for_each_cpu(cpu, mask) - cpum_cf_free_cpu(cpu); + cpum_cf_free_cpu(cpu, 1); break; } cpumask_set_cpu(cpu, mask); } + if (!rc) + cpu_cf_root.tskctx++; + mutex_unlock(&pmc_reserve_mutex); free_cpumask_var(mask); } else { - rc = cpum_cf_alloc_cpu(cpu); + mutex_lock(&pmc_reserve_mutex); + rc = cpum_cf_alloc_cpu(cpu, 1); + mutex_unlock(&pmc_reserve_mutex); } return rc; } +static int cpum_cf_alloc(int cpu) +{ + int rc; + + cpus_read_lock(); + rc = cpum_cf_alloc_cpuslocked(cpu); + cpus_read_unlock(); + return rc; +} + +static void cpum_cf_free_cpuslocked(int cpu) +{ + lockdep_assert_cpus_held(); + mutex_lock(&pmc_reserve_mutex); + if (cpu == -1) { + cpu_cf_root.tskctx--; + for_each_online_cpu(cpu) + cpum_cf_free_cpu(cpu, 1); + } else { + cpum_cf_free_cpu(cpu, 1); + } + mutex_unlock(&pmc_reserve_mutex); +} + static void cpum_cf_free(int cpu) { - if (cpu == -1) { - for_each_online_cpu(cpu) - cpum_cf_free_cpu(cpu); - } else { - cpum_cf_free_cpu(cpu); - } + cpus_read_lock(); + cpum_cf_free_cpuslocked(cpu); + cpus_read_unlock(); } #define CF_DIAG_CTRSET_DEF 0xfeef /* Counter set header mark */ @@ -1087,53 +1125,67 @@ static refcount_t cfset_opencnt = REFCOUNT_INIT(0); /* Access count */ static DEFINE_MUTEX(cfset_ctrset_mutex); /* - * CPU hotplug handles only /dev/hwctr device. - * For perf_event_open() the CPU hotplug handling is done on kernel common - * code: + * CPU hotplug handling: + * + * cpum_cf_prepare_cpu() and cpum_cf_dead_cpu() run while the new or dying + * CPU is offline. They create and remove the per CPU counter data for all + * users tracking every CPU (cpu == -1), that is perf_event_open() events + * with task context and /dev/hwctr device sessions. Each such user holds + * one reference to the per CPU counter data of each CPU. Therefore install + * and remove one reference per user, tracked in cpu_cf_root::tskctx. This + * guarantees the per CPU counter data exists before the new CPU executes + * its first task and is removed only after the dying CPU is gone. + * + * cpum_cf_online_cpu() and cpum_cf_offline_cpu() run while the new or + * dying CPU is online. They handle only the counter set state of open + * /dev/hwctr device sessions on that CPU. For perf_event_open() events + * nothing is done: * - CPU add: Nothing is done since a file descriptor can not be created * and returned to the user. * - CPU delete: Handled by common code via pmu_disable(), pmu_stop() and - * pmu_delete(). The event itself is removed when the file descriptor is - * closed. + * pmu_delete(). During task exit processing of grouped perf events + * triggered by CPU hotplug processing, pmu_disable() is called as part + * of perf context removal process. The event itself is removed when the + * event file descriptor is closed. */ +static int cpum_cf_prepare_cpu(unsigned int cpu) +{ + int rc = 0; + + mutex_lock(&pmc_reserve_mutex); + if (cpu_cf_root.tskctx) + rc = cpum_cf_alloc_cpu(cpu, cpu_cf_root.tskctx); + mutex_unlock(&pmc_reserve_mutex); + return rc; +} + +static int cpum_cf_dead_cpu(unsigned int cpu) +{ + mutex_lock(&pmc_reserve_mutex); + if (cpu_cf_root.tskctx) + cpum_cf_free_cpu(cpu, cpu_cf_root.tskctx); + mutex_unlock(&pmc_reserve_mutex); + return 0; +} + static int cfset_online_cpu(unsigned int cpu); static int cpum_cf_online_cpu(unsigned int cpu) { - int rc = 0; - - /* - * Ignore notification for perf_event_open(). - * Handle only /dev/hwctr device sessions. - */ mutex_lock(&cfset_ctrset_mutex); - if (refcount_read(&cfset_opencnt)) { - rc = cpum_cf_alloc_cpu(cpu); - if (!rc) - cfset_online_cpu(cpu); - } + if (refcount_read(&cfset_opencnt)) + cfset_online_cpu(cpu); mutex_unlock(&cfset_ctrset_mutex); - return rc; + return 0; } static int cfset_offline_cpu(unsigned int cpu); static int cpum_cf_offline_cpu(unsigned int cpu) { - /* - * During task exit processing of grouped perf events triggered by CPU - * hotplug processing, pmu_disable() is called as part of perf context - * removal process. Therefore do not trigger event removal now for - * perf_event_open() created events. Perf common code triggers event - * destruction when the event file descriptor is closed. - * - * Handle only /dev/hwctr device sessions. - */ mutex_lock(&cfset_ctrset_mutex); - if (refcount_read(&cfset_opencnt)) { + if (refcount_read(&cfset_opencnt)) cfset_offline_cpu(cpu); - cpum_cf_free_cpu(cpu); - } mutex_unlock(&cfset_ctrset_mutex); return 0; } @@ -1180,7 +1232,7 @@ static void cpumf_measurement_alert(struct ext_code ext_code, static int cfset_init(void); static int __init cpumf_pmu_init(void) { - int rc; + int state, rc; /* Extract counter measurement facility information */ if (!cpum_cf_avail() || qctri(&cpumf_ctr_info)) @@ -1222,11 +1274,24 @@ static int __init cpumf_pmu_init(void) cfset_init(); } + rc = cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, + "perf/s390/cf:prepare", + cpum_cf_prepare_cpu, cpum_cf_dead_cpu); + if (rc < 0) + goto out3; + state = rc; + rc = cpuhp_setup_state(CPUHP_AP_PERF_S390_CF_ONLINE, "perf/s390/cf:online", cpum_cf_online_cpu, cpum_cf_offline_cpu); - return rc; + if (rc < 0) + goto out4; + return 0; +out4: + cpuhp_remove_state(state); +out3: + perf_pmu_unregister(&cpumf_pmu); out2: debug_unregister_view(cf_dbg, &debug_sprintf_view); debug_unregister(cf_dbg); @@ -1382,6 +1447,7 @@ static void cfset_all_stop(struct cfset_request *req) */ static int cfset_release(struct inode *inode, struct file *file) { + cpus_read_lock(); mutex_lock(&cfset_ctrset_mutex); /* Open followed by close/exit has no private_data */ if (file->private_data) { @@ -1392,9 +1458,10 @@ static int cfset_release(struct inode *inode, struct file *file) } if (refcount_dec_and_test(&cfset_opencnt)) { /* Last close */ on_each_cpu(cfset_release_cpu, NULL, 1); - cpum_cf_free(-1); + cpum_cf_free_cpuslocked(-1); } mutex_unlock(&cfset_ctrset_mutex); + cpus_read_unlock(); return 0; } @@ -1413,15 +1480,17 @@ static int cfset_open(struct inode *inode, struct file *file) return -EPERM; file->private_data = NULL; + cpus_read_lock(); mutex_lock(&cfset_ctrset_mutex); if (!refcount_inc_not_zero(&cfset_opencnt)) { /* First open */ - rc = cpum_cf_alloc(-1); + rc = cpum_cf_alloc_cpuslocked(-1); if (!rc) { cfset_session_init(); refcount_set(&cfset_opencnt, 1); } } mutex_unlock(&cfset_ctrset_mutex); + cpus_read_unlock(); /* nonseekable_open() never fails */ return rc ?: nonseekable_open(inode, file);