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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-17 00:20:36 +0200 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-17 00:20:36 +0200 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /drivers/oprofile/buffer_sync.c | |
download | linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'drivers/oprofile/buffer_sync.c')
-rw-r--r-- | drivers/oprofile/buffer_sync.c | 547 |
1 files changed, 547 insertions, 0 deletions
diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c new file mode 100644 index 000000000000..55720dc6ec43 --- /dev/null +++ b/drivers/oprofile/buffer_sync.c @@ -0,0 +1,547 @@ +/** + * @file buffer_sync.c + * + * @remark Copyright 2002 OProfile authors + * @remark Read the file COPYING + * + * @author John Levon <levon@movementarian.org> + * + * 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/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 "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_t marked_cpus = CPU_MASK_NONE; +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. + */ +static int task_free_notify(struct notifier_block * self, unsigned long val, void * data) +{ + struct task_struct * task = data; + spin_lock(&task_mortuary); + list_add(&task->tasks, &dying_tasks); + spin_unlock(&task_mortuary); + 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(_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(_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 ? */ + down(&buffer_sem); + add_event_entry(ESCAPE_CODE); + add_event_entry(MODULE_LOADED_CODE); + up(&buffer_sem); +#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 end_sync(void) +{ + end_cpu_work(); + /* make sure we don't leak task structs */ + process_task_mortuary(); + process_task_mortuary(); +} + + +int sync_start(void) +{ + int err; + + start_cpu_work(); + + 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; + +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); +out1: + end_sync(); + goto out; +} + + +void sync_stop(void) +{ + 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); + end_sync(); +} + + +/* 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(struct dentry * dentry, + struct vfsmount * vfsmnt) +{ + unsigned long cookie; + + if (dentry->d_cookie) + return (unsigned long)dentry; + get_dcookie(dentry, vfsmnt, &cookie); + return cookie; +} + + +/* Look up the dcookie for the task's first VM_EXECUTABLE mapping, + * 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 = 0; + struct vm_area_struct * vma; + + if (!mm) + goto out; + + for (vma = mm->mmap; vma; vma = vma->vm_next) { + if (!vma->vm_file) + continue; + if (!(vma->vm_flags & VM_EXECUTABLE)) + continue; + cookie = fast_get_dcookie(vma->vm_file->f_dentry, + vma->vm_file->f_vfsmnt); + break; + } + +out: + 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. + */ +static unsigned long lookup_dcookie(struct mm_struct * mm, unsigned long addr, off_t * offset) +{ + unsigned long cookie = 0; + struct vm_area_struct * vma; + + for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) { + + if (!vma->vm_file) + continue; + + if (addr < vma->vm_start || addr >= vma->vm_end) + continue; + + cookie = fast_get_dcookie(vma->vm_file->f_dentry, + vma->vm_file->f_vfsmnt); + *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr - vma->vm_start; + break; + } + + return cookie; +} + + +static unsigned long last_cookie = ~0UL; + +static void add_cpu_switch(int i) +{ + add_event_entry(ESCAPE_CODE); + add_event_entry(CPU_SWITCH_CODE); + add_event_entry(i); + last_cookie = ~0UL; +} + +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_sample_entry(unsigned long offset, unsigned long event) +{ + add_event_entry(offset); + add_event_entry(event); +} + + +static int add_us_sample(struct mm_struct * mm, struct op_sample * s) +{ + unsigned long cookie; + off_t offset; + + cookie = lookup_dcookie(mm, s->eip, &offset); + + if (!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; +} + + +/* 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. + */ +static int +add_sample(struct mm_struct * mm, struct op_sample * s, int in_kernel) +{ + if (in_kernel) { + add_sample_entry(s->eip, s->event); + return 1; + } else if (mm) { + return add_us_sample(mm, s); + } else { + atomic_inc(&oprofile_stats.sample_lost_no_mm); + } + return 0; +} + + +static void release_mm(struct mm_struct * mm) +{ + if (!mm) + return; + up_read(&mm->mmap_sem); + mmput(mm); +} + + +static struct mm_struct * take_tasks_mm(struct task_struct * task) +{ + struct mm_struct * mm = get_task_mm(task); + if (mm) + down_read(&mm->mmap_sem); + return mm; +} + + +static inline int is_code(unsigned long val) +{ + return val == ESCAPE_CODE; +} + + +/* "acquire" as many cpu buffer slots as we can */ +static unsigned long get_slots(struct oprofile_cpu_buffer * b) +{ + unsigned long head = b->head_pos; + unsigned long tail = b->tail_pos; + + /* + * Subtle. This resets the persistent last_task + * and in_kernel values used for switching notes. + * BUT, there is a small window between reading + * head_pos, and this call, that means samples + * can appear at the new head position, but not + * be prefixed with the notes for switching + * kernel mode or a task switch. This small hole + * can lead to mis-attribution or samples where + * we don't know if it's in the kernel or not, + * at the start of an event buffer. + */ + cpu_buffer_reset(b); + + if (head >= tail) + return head - tail; + + return head + (b->buffer_size - tail); +} + + +static void increment_tail(struct oprofile_cpu_buffer * b) +{ + unsigned long new_tail = b->tail_pos + 1; + + rmb(); + + if (new_tail < b->buffer_size) + b->tail_pos = new_tail; + else + b->tail_pos = 0; +} + + +/* 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) +{ + struct list_head * pos; + struct list_head * pos2; + struct task_struct * task; + + spin_lock(&task_mortuary); + + list_for_each_safe(pos, pos2, &dead_tasks) { + task = list_entry(pos, struct task_struct, tasks); + list_del(&task->tasks); + free_task(task); + } + + list_for_each_safe(pos, pos2, &dying_tasks) { + task = list_entry(pos, struct task_struct, tasks); + list_del(&task->tasks); + list_add_tail(&task->tasks, &dead_tasks); + } + + spin_unlock(&task_mortuary); +} + + +static void mark_done(int cpu) +{ + int i; + + cpu_set(cpu, marked_cpus); + + for_each_online_cpu(i) { + if (!cpu_isset(i, marked_cpus)) + return; + } + + /* All CPUs have been processed at least once, + * we can process the mortuary once + */ + process_task_mortuary(); + + cpus_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 oprofile_cpu_buffer * cpu_buf = &cpu_buffer[cpu]; + struct mm_struct *mm = NULL; + struct task_struct * new; + unsigned long cookie = 0; + int in_kernel = 1; + unsigned int i; + sync_buffer_state state = sb_buffer_start; + unsigned long available; + + down(&buffer_sem); + + add_cpu_switch(cpu); + + /* Remember, only we can modify tail_pos */ + + available = get_slots(cpu_buf); + + for (i = 0; i < available; ++i) { + struct op_sample * s = &cpu_buf->buffer[cpu_buf->tail_pos]; + + if (is_code(s->eip)) { + if (s->event <= CPU_IS_KERNEL) { + /* kernel/userspace switch */ + in_kernel = s->event; + if (state == sb_buffer_start) + state = sb_sample_start; + add_kernel_ctx_switch(s->event); + } else if (s->event == CPU_TRACE_BEGIN) { + state = sb_bt_start; + add_trace_begin(); + } else { + struct mm_struct * oldmm = mm; + + /* userspace context switch */ + new = (struct task_struct *)s->event; + + release_mm(oldmm); + mm = take_tasks_mm(new); + if (mm != oldmm) + cookie = get_exec_dcookie(mm); + add_user_ctx_switch(new, cookie); + } + } else { + if (state >= sb_bt_start && + !add_sample(mm, s, in_kernel)) { + if (state == sb_bt_start) { + state = sb_bt_ignore; + atomic_inc(&oprofile_stats.bt_lost_no_mapping); + } + } + } + + increment_tail(cpu_buf); + } + release_mm(mm); + + mark_done(cpu); + + up(&buffer_sem); +} |