diff options
Diffstat (limited to 'drivers/oprofile/buffer_sync.c')
| -rw-r--r-- | drivers/oprofile/buffer_sync.c | 591 |
1 files changed, 591 insertions, 0 deletions
diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c new file mode 100644 index 000000000..ac27f3d3f --- /dev/null +++ b/drivers/oprofile/buffer_sync.c @@ -0,0 +1,591 @@ +/** + * @file buffer_sync.c + * + * @remark Copyright 2002-2009 OProfile authors + * @remark Read the file COPYING + * + * @author John Levon <levon@movementarian.org> + * @author Barry Kasindorf + * @author Robert Richter <robert.richter@amd.com> + * + * This is the core of the buffer management. Each + * CPU buffer is processed and entered into the + * global event buffer. Such processing is necessary + * in several circumstances, mentioned below. + * + * The processing does the job of converting the + * transitory EIP value into a persistent dentry/offset + * value that the profiler can record at its leisure. + * + * See fs/dcookies.c for a description of the dentry/offset + * objects. + */ + +#include <linux/file.h> +#include <linux/mm.h> +#include <linux/workqueue.h> +#include <linux/notifier.h> +#include <linux/dcookies.h> +#include <linux/profile.h> +#include <linux/module.h> +#include <linux/fs.h> +#include <linux/oprofile.h> +#include <linux/sched.h> +#include <linux/sched/mm.h> +#include <linux/sched/task.h> +#include <linux/gfp.h> + +#include "oprofile_stats.h" +#include "event_buffer.h" +#include "cpu_buffer.h" +#include "buffer_sync.h" + +static LIST_HEAD(dying_tasks); +static LIST_HEAD(dead_tasks); +static cpumask_var_t marked_cpus; +static DEFINE_SPINLOCK(task_mortuary); +static void process_task_mortuary(void); + +/* Take ownership of the task struct and place it on the + * list for processing. Only after two full buffer syncs + * does the task eventually get freed, because by then + * we are sure we will not reference it again. + * Can be invoked from softirq via RCU callback due to + * call_rcu() of the task struct, hence the _irqsave. + */ +static int +task_free_notify(struct notifier_block *self, unsigned long val, void *data) +{ + unsigned long flags; + struct task_struct *task = data; + spin_lock_irqsave(&task_mortuary, flags); + list_add(&task->tasks, &dying_tasks); + spin_unlock_irqrestore(&task_mortuary, flags); + return NOTIFY_OK; +} + + +/* The task is on its way out. A sync of the buffer means we can catch + * any remaining samples for this task. + */ +static int +task_exit_notify(struct notifier_block *self, unsigned long val, void *data) +{ + /* To avoid latency problems, we only process the current CPU, + * hoping that most samples for the task are on this CPU + */ + sync_buffer(raw_smp_processor_id()); + return 0; +} + + +/* The task is about to try a do_munmap(). We peek at what it's going to + * do, and if it's an executable region, process the samples first, so + * we don't lose any. This does not have to be exact, it's a QoI issue + * only. + */ +static int +munmap_notify(struct notifier_block *self, unsigned long val, void *data) +{ + unsigned long addr = (unsigned long)data; + struct mm_struct *mm = current->mm; + struct vm_area_struct *mpnt; + + down_read(&mm->mmap_sem); + + mpnt = find_vma(mm, addr); + if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) { + up_read(&mm->mmap_sem); + /* To avoid latency problems, we only process the current CPU, + * hoping that most samples for the task are on this CPU + */ + sync_buffer(raw_smp_processor_id()); + return 0; + } + + up_read(&mm->mmap_sem); + return 0; +} + + +/* We need to be told about new modules so we don't attribute to a previously + * loaded module, or drop the samples on the floor. + */ +static int +module_load_notify(struct notifier_block *self, unsigned long val, void *data) +{ +#ifdef CONFIG_MODULES + if (val != MODULE_STATE_COMING) + return 0; + + /* FIXME: should we process all CPU buffers ? */ + mutex_lock(&buffer_mutex); + add_event_entry(ESCAPE_CODE); + add_event_entry(MODULE_LOADED_CODE); + mutex_unlock(&buffer_mutex); +#endif + return 0; +} + + +static struct notifier_block task_free_nb = { + .notifier_call = task_free_notify, +}; + +static struct notifier_block task_exit_nb = { + .notifier_call = task_exit_notify, +}; + +static struct notifier_block munmap_nb = { + .notifier_call = munmap_notify, +}; + +static struct notifier_block module_load_nb = { + .notifier_call = module_load_notify, +}; + +static void free_all_tasks(void) +{ + /* make sure we don't leak task structs */ + process_task_mortuary(); + process_task_mortuary(); +} + +int sync_start(void) +{ + int err; + + if (!zalloc_cpumask_var(&marked_cpus, GFP_KERNEL)) + return -ENOMEM; + + err = task_handoff_register(&task_free_nb); + if (err) + goto out1; + err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb); + if (err) + goto out2; + err = profile_event_register(PROFILE_MUNMAP, &munmap_nb); + if (err) + goto out3; + err = register_module_notifier(&module_load_nb); + if (err) + goto out4; + + start_cpu_work(); + +out: + return err; +out4: + profile_event_unregister(PROFILE_MUNMAP, &munmap_nb); +out3: + profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb); +out2: + task_handoff_unregister(&task_free_nb); + free_all_tasks(); +out1: + free_cpumask_var(marked_cpus); + goto out; +} + + +void sync_stop(void) +{ + end_cpu_work(); + unregister_module_notifier(&module_load_nb); + profile_event_unregister(PROFILE_MUNMAP, &munmap_nb); + profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb); + task_handoff_unregister(&task_free_nb); + barrier(); /* do all of the above first */ + + flush_cpu_work(); + + free_all_tasks(); + free_cpumask_var(marked_cpus); +} + + +/* Optimisation. We can manage without taking the dcookie sem + * because we cannot reach this code without at least one + * dcookie user still being registered (namely, the reader + * of the event buffer). */ +static inline unsigned long fast_get_dcookie(const struct path *path) +{ + unsigned long cookie; + + if (path->dentry->d_flags & DCACHE_COOKIE) + return (unsigned long)path->dentry; + get_dcookie(path, &cookie); + return cookie; +} + + +/* Look up the dcookie for the task's mm->exe_file, + * which corresponds loosely to "application name". This is + * not strictly necessary but allows oprofile to associate + * shared-library samples with particular applications + */ +static unsigned long get_exec_dcookie(struct mm_struct *mm) +{ + unsigned long cookie = NO_COOKIE; + struct file *exe_file; + + if (!mm) + goto done; + + exe_file = get_mm_exe_file(mm); + if (!exe_file) + goto done; + + cookie = fast_get_dcookie(&exe_file->f_path); + fput(exe_file); +done: + return cookie; +} + + +/* Convert the EIP value of a sample into a persistent dentry/offset + * pair that can then be added to the global event buffer. We make + * sure to do this lookup before a mm->mmap modification happens so + * we don't lose track. + * + * The caller must ensure the mm is not nil (ie: not a kernel thread). + */ +static unsigned long +lookup_dcookie(struct mm_struct *mm, unsigned long addr, off_t *offset) +{ + unsigned long cookie = NO_COOKIE; + struct vm_area_struct *vma; + + down_read(&mm->mmap_sem); + for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) { + + if (addr < vma->vm_start || addr >= vma->vm_end) + continue; + + if (vma->vm_file) { + cookie = fast_get_dcookie(&vma->vm_file->f_path); + *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr - + vma->vm_start; + } else { + /* must be an anonymous map */ + *offset = addr; + } + + break; + } + + if (!vma) + cookie = INVALID_COOKIE; + up_read(&mm->mmap_sem); + + return cookie; +} + +static unsigned long last_cookie = INVALID_COOKIE; + +static void add_cpu_switch(int i) +{ + add_event_entry(ESCAPE_CODE); + add_event_entry(CPU_SWITCH_CODE); + add_event_entry(i); + last_cookie = INVALID_COOKIE; +} + +static void add_kernel_ctx_switch(unsigned int in_kernel) +{ + add_event_entry(ESCAPE_CODE); + if (in_kernel) + add_event_entry(KERNEL_ENTER_SWITCH_CODE); + else + add_event_entry(KERNEL_EXIT_SWITCH_CODE); +} + +static void +add_user_ctx_switch(struct task_struct const *task, unsigned long cookie) +{ + add_event_entry(ESCAPE_CODE); + add_event_entry(CTX_SWITCH_CODE); + add_event_entry(task->pid); + add_event_entry(cookie); + /* Another code for daemon back-compat */ + add_event_entry(ESCAPE_CODE); + add_event_entry(CTX_TGID_CODE); + add_event_entry(task->tgid); +} + + +static void add_cookie_switch(unsigned long cookie) +{ + add_event_entry(ESCAPE_CODE); + add_event_entry(COOKIE_SWITCH_CODE); + add_event_entry(cookie); +} + + +static void add_trace_begin(void) +{ + add_event_entry(ESCAPE_CODE); + add_event_entry(TRACE_BEGIN_CODE); +} + +static void add_data(struct op_entry *entry, struct mm_struct *mm) +{ + unsigned long code, pc, val; + unsigned long cookie; + off_t offset; + + if (!op_cpu_buffer_get_data(entry, &code)) + return; + if (!op_cpu_buffer_get_data(entry, &pc)) + return; + if (!op_cpu_buffer_get_size(entry)) + return; + + if (mm) { + cookie = lookup_dcookie(mm, pc, &offset); + + if (cookie == NO_COOKIE) + offset = pc; + if (cookie == INVALID_COOKIE) { + atomic_inc(&oprofile_stats.sample_lost_no_mapping); + offset = pc; + } + if (cookie != last_cookie) { + add_cookie_switch(cookie); + last_cookie = cookie; + } + } else + offset = pc; + + add_event_entry(ESCAPE_CODE); + add_event_entry(code); + add_event_entry(offset); /* Offset from Dcookie */ + + while (op_cpu_buffer_get_data(entry, &val)) + add_event_entry(val); +} + +static inline void add_sample_entry(unsigned long offset, unsigned long event) +{ + add_event_entry(offset); + add_event_entry(event); +} + + +/* + * Add a sample to the global event buffer. If possible the + * sample is converted into a persistent dentry/offset pair + * for later lookup from userspace. Return 0 on failure. + */ +static int +add_sample(struct mm_struct *mm, struct op_sample *s, int in_kernel) +{ + unsigned long cookie; + off_t offset; + + if (in_kernel) { + add_sample_entry(s->eip, s->event); + return 1; + } + + /* add userspace sample */ + + if (!mm) { + atomic_inc(&oprofile_stats.sample_lost_no_mm); + return 0; + } + + cookie = lookup_dcookie(mm, s->eip, &offset); + + if (cookie == INVALID_COOKIE) { + atomic_inc(&oprofile_stats.sample_lost_no_mapping); + return 0; + } + + if (cookie != last_cookie) { + add_cookie_switch(cookie); + last_cookie = cookie; + } + + add_sample_entry(offset, s->event); + + return 1; +} + + +static void release_mm(struct mm_struct *mm) +{ + if (!mm) + return; + mmput(mm); +} + +static inline int is_code(unsigned long val) +{ + return val == ESCAPE_CODE; +} + + +/* Move tasks along towards death. Any tasks on dead_tasks + * will definitely have no remaining references in any + * CPU buffers at this point, because we use two lists, + * and to have reached the list, it must have gone through + * one full sync already. + */ +static void process_task_mortuary(void) +{ + unsigned long flags; + LIST_HEAD(local_dead_tasks); + struct task_struct *task; + struct task_struct *ttask; + + spin_lock_irqsave(&task_mortuary, flags); + + list_splice_init(&dead_tasks, &local_dead_tasks); + list_splice_init(&dying_tasks, &dead_tasks); + + spin_unlock_irqrestore(&task_mortuary, flags); + + list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) { + list_del(&task->tasks); + free_task(task); + } +} + + +static void mark_done(int cpu) +{ + int i; + + cpumask_set_cpu(cpu, marked_cpus); + + for_each_online_cpu(i) { + if (!cpumask_test_cpu(i, marked_cpus)) + return; + } + + /* All CPUs have been processed at least once, + * we can process the mortuary once + */ + process_task_mortuary(); + + cpumask_clear(marked_cpus); +} + + +/* FIXME: this is not sufficient if we implement syscall barrier backtrace + * traversal, the code switch to sb_sample_start at first kernel enter/exit + * switch so we need a fifth state and some special handling in sync_buffer() + */ +typedef enum { + sb_bt_ignore = -2, + sb_buffer_start, + sb_bt_start, + sb_sample_start, +} sync_buffer_state; + +/* Sync one of the CPU's buffers into the global event buffer. + * Here we need to go through each batch of samples punctuated + * by context switch notes, taking the task's mmap_sem and doing + * lookup in task->mm->mmap to convert EIP into dcookie/offset + * value. + */ +void sync_buffer(int cpu) +{ + struct mm_struct *mm = NULL; + struct mm_struct *oldmm; + unsigned long val; + struct task_struct *new; + unsigned long cookie = 0; + int in_kernel = 1; + sync_buffer_state state = sb_buffer_start; + unsigned int i; + unsigned long available; + unsigned long flags; + struct op_entry entry; + struct op_sample *sample; + + mutex_lock(&buffer_mutex); + + add_cpu_switch(cpu); + + op_cpu_buffer_reset(cpu); + available = op_cpu_buffer_entries(cpu); + + for (i = 0; i < available; ++i) { + sample = op_cpu_buffer_read_entry(&entry, cpu); + if (!sample) + break; + + if (is_code(sample->eip)) { + flags = sample->event; + if (flags & TRACE_BEGIN) { + state = sb_bt_start; + add_trace_begin(); + } + if (flags & KERNEL_CTX_SWITCH) { + /* kernel/userspace switch */ + in_kernel = flags & IS_KERNEL; + if (state == sb_buffer_start) + state = sb_sample_start; + add_kernel_ctx_switch(flags & IS_KERNEL); + } + if (flags & USER_CTX_SWITCH + && op_cpu_buffer_get_data(&entry, &val)) { + /* userspace context switch */ + new = (struct task_struct *)val; + oldmm = mm; + release_mm(oldmm); + mm = get_task_mm(new); + if (mm != oldmm) + cookie = get_exec_dcookie(mm); + add_user_ctx_switch(new, cookie); + } + if (op_cpu_buffer_get_size(&entry)) + add_data(&entry, mm); + continue; + } + + if (state < sb_bt_start) + /* ignore sample */ + continue; + + if (add_sample(mm, sample, in_kernel)) + continue; + + /* ignore backtraces if failed to add a sample */ + if (state == sb_bt_start) { + state = sb_bt_ignore; + atomic_inc(&oprofile_stats.bt_lost_no_mapping); + } + } + release_mm(mm); + + mark_done(cpu); + + mutex_unlock(&buffer_mutex); +} + +/* The function can be used to add a buffer worth of data directly to + * the kernel buffer. The buffer is assumed to be a circular buffer. + * Take the entries from index start and end at index end, wrapping + * at max_entries. + */ +void oprofile_put_buff(unsigned long *buf, unsigned int start, + unsigned int stop, unsigned int max) +{ + int i; + + i = start; + + mutex_lock(&buffer_mutex); + while (i != stop) { + add_event_entry(buf[i++]); + + if (i >= max) + i = 0; + } + + mutex_unlock(&buffer_mutex); +} + |