/** * @file cpu_buffer.c * * @remark Copyright 2002-2009 OProfile authors * @remark Read the file COPYING * * @author John Levon <levon@movementarian.org> * @author Barry Kasindorf <barry.kasindorf@amd.com> * @author Robert Richter <robert.richter@amd.com> * * Each CPU has a local buffer that stores PC value/event * pairs. We also log context switches when we notice them. * Eventually each CPU's buffer is processed into the global * event buffer by sync_buffer(). * * We use a local buffer for two reasons: an NMI or similar * interrupt cannot synchronise, and high sampling rates * would lead to catastrophic global synchronisation if * a global buffer was used. */ #include <linux/sched.h> #include <linux/oprofile.h> #include <linux/vmalloc.h> #include <linux/errno.h> #include "event_buffer.h" #include "cpu_buffer.h" #include "buffer_sync.h" #include "oprof.h" #define OP_BUFFER_FLAGS 0 /* * Read and write access is using spin locking. Thus, writing to the * buffer by NMI handler (x86) could occur also during critical * sections when reading the buffer. To avoid this, there are 2 * buffers for independent read and write access. Read access is in * process context only, write access only in the NMI handler. If the * read buffer runs empty, both buffers are swapped atomically. There * is potentially a small window during swapping where the buffers are * disabled and samples could be lost. * * Using 2 buffers is a little bit overhead, but the solution is clear * and does not require changes in the ring buffer implementation. It * can be changed to a single buffer solution when the ring buffer * access is implemented as non-locking atomic code. */ static struct ring_buffer *op_ring_buffer_read; static struct ring_buffer *op_ring_buffer_write; DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer); static void wq_sync_buffer(struct work_struct *work); #define DEFAULT_TIMER_EXPIRE (HZ / 10) static int work_enabled; unsigned long oprofile_get_cpu_buffer_size(void) { return oprofile_cpu_buffer_size; } void oprofile_cpu_buffer_inc_smpl_lost(void) { struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); cpu_buf->sample_lost_overflow++; } void free_cpu_buffers(void) { if (op_ring_buffer_read) ring_buffer_free(op_ring_buffer_read); op_ring_buffer_read = NULL; if (op_ring_buffer_write) ring_buffer_free(op_ring_buffer_write); op_ring_buffer_write = NULL; } #define RB_EVENT_HDR_SIZE 4 int alloc_cpu_buffers(void) { int i; unsigned long buffer_size = oprofile_cpu_buffer_size; unsigned long byte_size = buffer_size * (sizeof(struct op_sample) + RB_EVENT_HDR_SIZE); op_ring_buffer_read = ring_buffer_alloc(byte_size, OP_BUFFER_FLAGS); if (!op_ring_buffer_read) goto fail; op_ring_buffer_write = ring_buffer_alloc(byte_size, OP_BUFFER_FLAGS); if (!op_ring_buffer_write) goto fail; for_each_possible_cpu(i) { struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i); b->last_task = NULL; b->last_is_kernel = -1; b->tracing = 0; b->buffer_size = buffer_size; b->sample_received = 0; b->sample_lost_overflow = 0; b->backtrace_aborted = 0; b->sample_invalid_eip = 0; b->cpu = i; INIT_DELAYED_WORK(&b->work, wq_sync_buffer); } return 0; fail: free_cpu_buffers(); return -ENOMEM; } void start_cpu_work(void) { int i; work_enabled = 1; for_each_online_cpu(i) { struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i); /* * Spread the work by 1 jiffy per cpu so they dont all * fire at once. */ schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i); } } void end_cpu_work(void) { int i; work_enabled = 0; for_each_online_cpu(i) { struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i); cancel_delayed_work(&b->work); } flush_scheduled_work(); } /* * This function prepares the cpu buffer to write a sample. * * Struct op_entry is used during operations on the ring buffer while * struct op_sample contains the data that is stored in the ring * buffer. Struct entry can be uninitialized. The function reserves a * data array that is specified by size. Use * op_cpu_buffer_write_commit() after preparing the sample. In case of * errors a null pointer is returned, otherwise the pointer to the * sample. * */ struct op_sample *op_cpu_buffer_write_reserve(struct op_entry *entry, unsigned long size) { entry->event = ring_buffer_lock_reserve (op_ring_buffer_write, sizeof(struct op_sample) + size * sizeof(entry->sample->data[0])); if (entry->event) entry->sample = ring_buffer_event_data(entry->event); else entry->sample = NULL; if (!entry->sample) return NULL; entry->size = size; entry->data = entry->sample->data; return entry->sample; } int op_cpu_buffer_write_commit(struct op_entry *entry) { return ring_buffer_unlock_commit(op_ring_buffer_write, entry->event); } struct op_sample *op_cpu_buffer_read_entry(struct op_entry *entry, int cpu) { struct ring_buffer_event *e; e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL); if (e) goto event; if (ring_buffer_swap_cpu(op_ring_buffer_read, op_ring_buffer_write, cpu)) return NULL; e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL); if (e) goto event; return NULL; event: entry->event = e; entry->sample = ring_buffer_event_data(e); entry->size = (ring_buffer_event_length(e) - sizeof(struct op_sample)) / sizeof(entry->sample->data[0]); entry->data = entry->sample->data; return entry->sample; } unsigned long op_cpu_buffer_entries(int cpu) { return ring_buffer_entries_cpu(op_ring_buffer_read, cpu) + ring_buffer_entries_cpu(op_ring_buffer_write, cpu); } static int op_add_code(struct oprofile_cpu_buffer *cpu_buf, unsigned long backtrace, int is_kernel, struct task_struct *task) { struct op_entry entry; struct op_sample *sample; unsigned long flags; int size; flags = 0; if (backtrace) flags |= TRACE_BEGIN; /* notice a switch from user->kernel or vice versa */ is_kernel = !!is_kernel; if (cpu_buf->last_is_kernel != is_kernel) { cpu_buf->last_is_kernel = is_kernel; flags |= KERNEL_CTX_SWITCH; if (is_kernel) flags |= IS_KERNEL; } /* notice a task switch */ if (cpu_buf->last_task != task) { cpu_buf->last_task = task; flags |= USER_CTX_SWITCH; } if (!flags) /* nothing to do */ return 0; if (flags & USER_CTX_SWITCH) size = 1; else size = 0; sample = op_cpu_buffer_write_reserve(&entry, size); if (!sample) return -ENOMEM; sample->eip = ESCAPE_CODE; sample->event = flags; if (size) op_cpu_buffer_add_data(&entry, (unsigned long)task); op_cpu_buffer_write_commit(&entry); return 0; } static inline int op_add_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc, unsigned long event) { struct op_entry entry; struct op_sample *sample; sample = op_cpu_buffer_write_reserve(&entry, 0); if (!sample) return -ENOMEM; sample->eip = pc; sample->event = event; return op_cpu_buffer_write_commit(&entry); } /* * This must be safe from any context. * * is_kernel is needed because on some architectures you cannot * tell if you are in kernel or user space simply by looking at * pc. We tag this in the buffer by generating kernel enter/exit * events whenever is_kernel changes */ static int log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc, unsigned long backtrace, int is_kernel, unsigned long event) { cpu_buf->sample_received++; if (pc == ESCAPE_CODE) { cpu_buf->sample_invalid_eip++; return 0; } if (op_add_code(cpu_buf, backtrace, is_kernel, current)) goto fail; if (op_add_sample(cpu_buf, pc, event)) goto fail; return 1; fail: cpu_buf->sample_lost_overflow++; return 0; } static inline void oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf) { cpu_buf->tracing = 1; } static inline void oprofile_end_trace(struct oprofile_cpu_buffer *cpu_buf) { cpu_buf->tracing = 0; } static inline void __oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs, unsigned long event, int is_kernel) { struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); unsigned long backtrace = oprofile_backtrace_depth; /* * if log_sample() fail we can't backtrace since we lost the * source of this event */ if (!log_sample(cpu_buf, pc, backtrace, is_kernel, event)) /* failed */ return; if (!backtrace) return; oprofile_begin_trace(cpu_buf); oprofile_ops.backtrace(regs, backtrace); oprofile_end_trace(cpu_buf); } void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs, unsigned long event, int is_kernel) { __oprofile_add_ext_sample(pc, regs, event, is_kernel); } void oprofile_add_sample(struct pt_regs * const regs, unsigned long event) { int is_kernel = !user_mode(regs); unsigned long pc = profile_pc(regs); __oprofile_add_ext_sample(pc, regs, event, is_kernel); } /* * Add samples with data to the ring buffer. * * Use oprofile_add_data(&entry, val) to add data and * oprofile_write_commit(&entry) to commit the sample. */ void oprofile_write_reserve(struct op_entry *entry, struct pt_regs * const regs, unsigned long pc, int code, int size) { struct op_sample *sample; int is_kernel = !user_mode(regs); struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); cpu_buf->sample_received++; /* no backtraces for samples with data */ if (op_add_code(cpu_buf, 0, is_kernel, current)) goto fail; sample = op_cpu_buffer_write_reserve(entry, size + 2); if (!sample) goto fail; sample->eip = ESCAPE_CODE; sample->event = 0; /* no flags */ op_cpu_buffer_add_data(entry, code); op_cpu_buffer_add_data(entry, pc); return; fail: entry->event = NULL; cpu_buf->sample_lost_overflow++; } int oprofile_add_data(struct op_entry *entry, unsigned long val) { if (!entry->event) return 0; return op_cpu_buffer_add_data(entry, val); } int oprofile_write_commit(struct op_entry *entry) { if (!entry->event) return -EINVAL; return op_cpu_buffer_write_commit(entry); } void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event) { struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); log_sample(cpu_buf, pc, 0, is_kernel, event); } void oprofile_add_trace(unsigned long pc) { struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); if (!cpu_buf->tracing) return; /* * broken frame can give an eip with the same value as an * escape code, abort the trace if we get it */ if (pc == ESCAPE_CODE) goto fail; if (op_add_sample(cpu_buf, pc, 0)) goto fail; return; fail: cpu_buf->tracing = 0; cpu_buf->backtrace_aborted++; return; } /* * This serves to avoid cpu buffer overflow, and makes sure * the task mortuary progresses * * By using schedule_delayed_work_on and then schedule_delayed_work * we guarantee this will stay on the correct cpu */ static void wq_sync_buffer(struct work_struct *work) { struct oprofile_cpu_buffer *b = container_of(work, struct oprofile_cpu_buffer, work.work); if (b->cpu != smp_processor_id()) { printk(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n", smp_processor_id(), b->cpu); if (!cpu_online(b->cpu)) { cancel_delayed_work(&b->work); return; } } sync_buffer(b->cpu); /* don't re-add the work if we're shutting down */ if (work_enabled) schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE); }