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Signed-off-by: Neeraj Upadhyay --- .../admin-guide/kernel-parameters.txt | 57 +++ lib/Kconfig.debug | 9 + lib/Makefile | 1 + lib/percpu-refcount-torture.c | 367 ++++++++++++++++++ lib/percpu-refcount.c | 49 ++- lib/percpu-refcount.h | 6 + 6 files changed, 483 insertions(+), 6 deletions(-) create mode 100644 lib/percpu-refcount-torture.c create mode 100644 lib/percpu-refcount.h diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0f02a1b04fe9..225f2dac294d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4677,6 +4677,63 @@ Default: 5000 ms + percpu_refcount_torture.busted_early_ref_release= [KNL] + Enable testing buggy release of percpu ref while + there are active users. Used for testing failure + scenarios in the test. + + Default: 0 (disabled) + + percpu_refcount_torture.busted_late_ref_release= [KNL] + Enable testing buggy non-zero reference count after + all ref users have dropped their reference. Used for + testing failure scenarios in the test. + + Default: 0 (disabled) + + percpu_refcount_torture.delay_us= [KNL] + Delay (in us) between reference increment and decrement + operations of ref users. + + Default: 10 + + percpu_refcount_torture.niterations= [KNL] + Number of iterations of ref increment and decrement by + ref users. + + Default: 100 + + percpu_refcount_torture.nrefs= [KNL] + Number of percpu ref instances. + + Default: 2 + + percpu_refcount_torture.nusers= [KNL] + Number of percpu ref user threads which increment and + decrement a percpu ref. + + Default: 2 + + percpu_refcount_torture.onoff_holdoff= [KNL] + Set time (s) after boot for CPU-hotplug testing. + + Default: 0 + + percpu_refcount_torture.onoff_interval= [KNL] + Set time (jiffies) between CPU-hotplug operations, + or zero to disable CPU-hotplug testing. + + percpu_refcount_torture.stutter= [KNL] + Set wait time (jiffies) between two iterations of + percpu ref operations. + + Default: 0 + + percpu_refcount_torture.verbose= [KNL] + Enable additional printk() statements. + + Default: 0 (Disabled) + pirq= [SMP,APIC] Manual mp-table setup See Documentation/arch/x86/i386/IO-APIC.rst. diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index a30c03a66172..7e0117e01f05 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1611,6 +1611,15 @@ config SCF_TORTURE_TEST module may be built after the fact on the running kernel to be tested, if desired. +config PERCPU_REFCOUNT_TORTURE_TEST + tristate "torture tests for percpu refcount" + select TORTURE_TEST + help + This options provides a kernel module that runs percpu + refcount torture tests for managed percpu refs. The kernel + module may be built after the fact on the running kernel + to be tested, if desired. + config CSD_LOCK_WAIT_DEBUG bool "Debugging for csd_lock_wait(), called from smp_call_function*()" depends on DEBUG_KERNEL diff --git a/lib/Makefile b/lib/Makefile index 322bb127b4dc..d0286f7dfb37 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -50,6 +50,7 @@ obj-y += bcd.o sort.o parser.o debug_locks.o random32.o \ once.o refcount.o rcuref.o usercopy.o errseq.o bucket_locks.o \ generic-radix-tree.o bitmap-str.o obj-$(CONFIG_STRING_KUNIT_TEST) += string_kunit.o +obj-$(CONFIG_PERCPU_REFCOUNT_TORTURE_TEST) += percpu-refcount-torture.o obj-y += string_helpers.o obj-$(CONFIG_STRING_HELPERS_KUNIT_TEST) += string_helpers_kunit.o obj-y += hexdump.o diff --git a/lib/percpu-refcount-torture.c b/lib/percpu-refcount-torture.c new file mode 100644 index 000000000000..686f5a228b40 --- /dev/null +++ b/lib/percpu-refcount-torture.c @@ -0,0 +1,367 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include +#include +#include +#include +#include + +#include "percpu-refcount.h" + +static int busted_early_ref_release; +module_param(busted_early_ref_release, int, 0444); +MODULE_PARM_DESC(busted_early_ref_release, + "Enable busted premature release of ref (default = 0), 0 = disable"); + +static int busted_late_ref_release; +module_param(busted_late_ref_release, int, 0444); +MODULE_PARM_DESC(busted_late_ref_release, + "Enable busted late release of ref (default = 0), 0 = disable"); + +static long delay_us = 10; +module_param(delay_us, long, 0444); +MODULE_PARM_DESC(delay_us, + "delay between reader refcount operations in microseconds (default = 10)"); + +static long nrefs = 2; +module_param(nrefs, long, 0444); +MODULE_PARM_DESC(nrefs, "Number of percpu refs (default = 2)"); + +static long niterations = 100; +module_param(niterations, long, 0444); +MODULE_PARM_DESC(niterations, + "Number of iterations of ref increment and decrement (default = 100)"); + +static long nusers = 2; +module_param(nusers, long, 0444); +MODULE_PARM_DESC(nusers, "Number of refcount users (default = 2)"); + +static int onoff_holdoff; +module_param(onoff_holdoff, int, 0444); +MODULE_PARM_DESC(onoff_holdoff, "Time after boot before CPU hotplugs (seconds)"); + +static int onoff_interval; +module_param(onoff_interval, int, 0444); +MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (jiffies), 0=disable"); + +static int stutter; +module_param(stutter, int, 0444); +MODULE_PARM_DESC(stutter, "Stutter period in jiffies (default = 0), 0 = disable"); + +static int verbose = 1; +module_param(verbose, int, 0444); +MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s"); + +static struct task_struct **ref_user_tasks; +static struct task_struct *ref_manager_task; +static struct task_struct **busted_early_release_tasks; +static struct task_struct **busted_late_release_tasks; + +static struct percpu_ref *refs; +static long *num_per_ref_users; + +static atomic_t running; +static atomic_t *ref_running; + +static char *torture_type = "percpu-refcount"; + +static int percpu_ref_manager_thread(void *data) +{ + int i; + + while (atomic_read(&running) != 0) { + percpu_ref_test_flush_release_work(); + stutter_wait("percpu_ref_manager_thread"); + } + /* Ensure ordering with ref users */ + smp_mb(); + + percpu_ref_test_flush_release_work(); + + for (i = 0; i < nrefs; i++) { + WARN(percpu_ref_test_is_percpu(&refs[i]), + "!!! released ref %d should be in atomic mode", i); + WARN(!percpu_ref_is_zero(&refs[i]), + "!!! released ref %d should have 0 refcount", i); + } + + do { + stutter_wait("percpu_ref_manager_thread"); + } while (!torture_must_stop()); + + torture_kthread_stopping("percpu_ref_manager_thread"); + + return 0; +} + +static int percpu_ref_test_thread(void *data) +{ + struct percpu_ref *ref = (struct percpu_ref *)data; + int i = 0; + + percpu_ref_get(ref); + + do { + percpu_ref_get(ref); + udelay(delay_us); + percpu_ref_put(ref); + stutter_wait("percpu_ref_test_thread"); + i++; + } while (i < niterations); + + atomic_dec(&ref_running[ref - refs]); + /* Order ref release with ref_running[ref_idx] == 0 */ + smp_mb(); + percpu_ref_put(ref); + /* Order ref decrement with running == 0 */ + smp_mb(); + atomic_dec(&running); + + do { + stutter_wait("percpu_ref_test_thread"); + } while (!torture_must_stop()); + + torture_kthread_stopping("percpu_ref_test_thread"); + + return 0; +} + +static int percpu_ref_busted_early_thread(void *data) +{ + struct percpu_ref *ref = (struct percpu_ref *)data; + int ref_idx = ref - refs; + int i = 0, j; + + do { + /* Extra ref put momemtarily */ + for (j = 0; j < num_per_ref_users[ref_idx]; j++) + percpu_ref_put(ref); + stutter_wait("percpu_ref_busted_early_thread"); + for (j = 0; j < num_per_ref_users[ref_idx]; j++) + percpu_ref_get(ref); + i++; + stutter_wait("percpu_ref_busted_early_thread"); + } while (i < niterations * 10); + + do { + stutter_wait("percpu_ref_busted_early_thread"); + } while (!torture_must_stop()); + + torture_kthread_stopping("percpu_ref_busted_early_thread"); + + return 0; +} + +static int percpu_ref_busted_late_thread(void *data) +{ + struct percpu_ref *ref = (struct percpu_ref *)data; + int i = 0; + + do { + /* Extra ref get momemtarily */ + percpu_ref_get(ref); + stutter_wait("percpu_ref_busted_late_thread"); + percpu_ref_put(ref); + i++; + } while (i < niterations); + + do { + stutter_wait("percpu_ref_busted_late_thread"); + } while (!torture_must_stop()); + + torture_kthread_stopping("percpu_ref_busted_late_thread"); + + return 0; +} + +static void percpu_ref_test_cleanup(void) +{ + int i; + + if (torture_cleanup_begin()) + return; + + if (busted_late_release_tasks) { + for (i = 0; i < nrefs; i++) + torture_stop_kthread(busted_late_task, busted_late_release_tasks[i]); + kfree(busted_late_release_tasks); + busted_late_release_tasks = NULL; + } + + if (busted_early_release_tasks) { + for (i = 0; i < nrefs; i++) + torture_stop_kthread(busted_early_task, busted_early_release_tasks[i]); + kfree(busted_early_release_tasks); + busted_early_release_tasks = NULL; + } + + if (ref_manager_task) { + torture_stop_kthread(ref_manager, ref_manager_task); + ref_manager_task = NULL; + } + + if (ref_user_tasks) { + for (i = 0; i < nusers; i++) + torture_stop_kthread(ref_user, ref_user_tasks[i]); + kfree(ref_user_tasks); + ref_user_tasks = NULL; + } + + kfree(ref_running); + ref_running = NULL; + + kfree(num_per_ref_users); + num_per_ref_users = NULL; + + if (refs) { + for (i = 0; i < nrefs; i++) + percpu_ref_exit(&refs[i]); + kfree(refs); + refs = NULL; + } + + torture_cleanup_end(); +} + +static void percpu_ref_test_release(struct percpu_ref *ref) +{ + WARN(!!atomic_add_return(0, &ref_running[ref-refs]), "!!! Premature ref release"); +} + +static int __init percpu_ref_torture_init(void) +{ + DEFINE_TORTURE_RANDOM(rand); + struct torture_random_state *trsp = &rand; + int flags; + int err; + int ref_idx; + int i; + + if (!torture_init_begin("percpu-refcount", verbose)) + return -EBUSY; + + atomic_set(&running, nusers); + /* Order @running with later increment and decrement operations */ + smp_mb(); + + refs = kcalloc(nrefs, sizeof(refs[0]), GFP_KERNEL); + if (!refs) { + TOROUT_ERRSTRING("out of memory"); + err = -ENOMEM; + goto init_err; + } + for (i = 0; i < nrefs; i++) { + flags = torture_random(trsp) & 1 ? PERCPU_REF_INIT_ATOMIC : PERCPU_REF_REL_MANAGED; + err = percpu_ref_init(&refs[i], percpu_ref_test_release, + flags, GFP_KERNEL); + if (err) + goto init_err; + if (!(flags & PERCPU_REF_REL_MANAGED)) + percpu_ref_switch_to_managed(&refs[i]); + } + + num_per_ref_users = kcalloc(nrefs, sizeof(num_per_ref_users[0]), GFP_KERNEL); + if (!num_per_ref_users) { + TOROUT_ERRSTRING("out of memory"); + err = -ENOMEM; + goto init_err; + } + for (i = 0; i < nrefs; i++) + num_per_ref_users[i] = 0; + + ref_user_tasks = kcalloc(nusers, sizeof(ref_user_tasks[0]), GFP_KERNEL); + if (!ref_user_tasks) { + TOROUT_ERRSTRING("out of memory"); + err = -ENOMEM; + goto init_err; + } + + ref_running = kcalloc(nrefs, sizeof(ref_running[0]), GFP_KERNEL); + if (!ref_running) { + TOROUT_ERRSTRING("out of memory"); + err = -ENOMEM; + goto init_err; + } + + for (i = 0; i < nusers; i++) { + ref_idx = torture_random(trsp) % nrefs; + atomic_inc(&ref_running[ref_idx]); + num_per_ref_users[ref_idx]++; + /* Order increments with subquent reads */ + smp_mb(); + err = torture_create_kthread(percpu_ref_test_thread, + &refs[ref_idx], ref_user_tasks[i]); + if (torture_init_error(err)) + goto init_err; + } + + err = torture_create_kthread(percpu_ref_manager_thread, NULL, ref_manager_task); + if (torture_init_error(err)) + goto init_err; + + /* Drop initial reference, after test threads have started running */ + udelay(1); + for (i = 0; i < nrefs; i++) + percpu_ref_put(&refs[i]); + + + if (busted_early_ref_release) { + busted_early_release_tasks = kcalloc(nrefs, + sizeof(busted_early_release_tasks[0]), + GFP_KERNEL); + if (!busted_early_release_tasks) { + TOROUT_ERRSTRING("out of memory"); + err = -ENOMEM; + goto init_err; + } + for (i = 0; i < nrefs; i++) { + err = torture_create_kthread(percpu_ref_busted_early_thread, + &refs[i], busted_early_release_tasks[i]); + if (torture_init_error(err)) + goto init_err; + } + } + + if (busted_late_ref_release) { + busted_late_release_tasks = kcalloc(nrefs, sizeof(busted_late_release_tasks[0]), + GFP_KERNEL); + if (!busted_late_release_tasks) { + TOROUT_ERRSTRING("out of memory"); + err = -ENOMEM; + goto init_err; + } + for (i = 0; i < nrefs; i++) { + err = torture_create_kthread(percpu_ref_busted_late_thread, + &refs[i], busted_late_release_tasks[i]); + if (torture_init_error(err)) + goto init_err; + } + } + if (stutter) { + err = torture_stutter_init(stutter, stutter); + if (torture_init_error(err)) + goto init_err; + } + + err = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, NULL); + if (torture_init_error(err)) + goto init_err; + + torture_init_end(); + return 0; +init_err: + torture_init_end(); + percpu_ref_test_cleanup(); + return err; +} + +static void __exit percpu_ref_torture_exit(void) +{ + percpu_ref_test_cleanup(); +} + +module_init(percpu_ref_torture_init); +module_exit(percpu_ref_torture_exit); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("percpu refcount torture test"); diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index 7b97f9728c5b..7d0c85c7ce57 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -11,6 +11,8 @@ #include #include +#include "percpu-refcount.h" + /* * Initially, a percpu refcount is just a set of percpu counters. Initially, we * don't try to detect the ref hitting 0 - which means that get/put can just @@ -677,6 +679,7 @@ static void percpu_ref_release_work_fn(struct work_struct *work) struct percpu_ref *ref; int count = 0; bool held; + struct llist_node *last_node = READ_ONCE(last_percpu_ref_node); first = READ_ONCE(percpu_ref_manage_head.first); if (!first) @@ -711,7 +714,7 @@ static void percpu_ref_release_work_fn(struct work_struct *work) * +----------+ +------+ +------+ +------+ +------+ * */ - if (last_percpu_ref_node == NULL || last_percpu_ref_node->next == NULL) { + if (last_node == NULL || last_node->next == NULL) { retry_sentinel_get: sen_node = percpu_ref_get_sen_node(); /* @@ -741,11 +744,10 @@ static void percpu_ref_release_work_fn(struct work_struct *work) head = prev->next; } } else { - prev = last_percpu_ref_node; + prev = last_node; head = prev->next; } - last_percpu_ref_node = NULL; llist_for_each_safe(pos, next, head) { /* Free sentinel node which is present in the list */ if (percpu_ref_is_sen_node(pos)) { @@ -773,18 +775,53 @@ static void percpu_ref_release_work_fn(struct work_struct *work) continue; __percpu_ref_switch_to_percpu_checked(ref, false); count++; - if (count == max_scan_count) { - last_percpu_ref_node = pos; - break; + if (count == READ_ONCE(max_scan_count)) { + WRITE_ONCE(last_percpu_ref_node, pos); + goto queue_release_work; } prev = pos; } + WRITE_ONCE(last_percpu_ref_node, NULL); queue_release_work: queue_delayed_work(percpu_ref_release_wq, &percpu_ref_release_work, scan_interval); } +bool percpu_ref_test_is_percpu(struct percpu_ref *ref) +{ + unsigned long __percpu *percpu_count; + + return __ref_is_percpu(ref, &percpu_count); +} +EXPORT_SYMBOL_GPL(percpu_ref_test_is_percpu); + +void percpu_ref_test_flush_release_work(void) +{ + int max_flush = READ_ONCE(max_scan_count); + int max_count = 1000; + + /* Complete any executing release work */ + flush_delayed_work(&percpu_ref_release_work); + /* Scan till the end of the llist */ + WRITE_ONCE(max_scan_count, INT_MAX); + /* max scan count update visible to release work */ + smp_mb(); + flush_delayed_work(&percpu_ref_release_work); + /* max scan count update visible to release work */ + smp_mb(); + WRITE_ONCE(max_scan_count, 1); + /* max scan count update visible to work */ + smp_mb(); + flush_delayed_work(&percpu_ref_release_work); + while (READ_ONCE(last_percpu_ref_node) != NULL && max_count--) + flush_delayed_work(&percpu_ref_release_work); + /* max scan count update visible to work */ + smp_mb(); + WRITE_ONCE(max_scan_count, max_flush); +} +EXPORT_SYMBOL_GPL(percpu_ref_test_flush_release_work); + static __init int percpu_ref_setup(void) { percpu_ref_release_wq = alloc_workqueue("percpu_ref_release_wq", diff --git a/lib/percpu-refcount.h b/lib/percpu-refcount.h new file mode 100644 index 000000000000..be2ac0411194 --- /dev/null +++ b/lib/percpu-refcount.h @@ -0,0 +1,6 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +#ifndef __LIB_REFCOUNT_H +#define __LIB_REFCOUNT_H +bool percpu_ref_test_is_percpu(struct percpu_ref *ref); +void percpu_ref_test_flush_release_work(void); +#endif