perf record: Fix fast task-exit race

[mirror_ubuntu-bionic-kernel.git] / tools / perf / builtin-record.c

/*
 * builtin-record.c
 *
 * Builtin record command: Record the profile of a workload
 * (or a CPU, or a PID) into the perf.data output file - for
 * later analysis via perf report.
 */
#include "builtin.h"

#include "perf.h"

#include "util/util.h"
#include "util/parse-options.h"
#include "util/parse-events.h"
#include "util/string.h"

#include <unistd.h>
#include <sched.h>

#define ALIGN(x, a)             __ALIGN_MASK(x, (typeof(x))(a)-1)
#define __ALIGN_MASK(x, mask)   (((x)+(mask))&~(mask))

static int                      fd[MAX_NR_CPUS][MAX_COUNTERS];

static long                     default_interval                = 100000;

static int                      nr_cpus                         = 0;
static unsigned int             page_size;
static unsigned int             mmap_pages                      = 128;
static int                      freq                            = 0;
static int                      output;
static const char               *output_name                    = "perf.data";
static int                      group                           = 0;
static unsigned int             realtime_prio                   = 0;
static int                      system_wide                     = 0;
static pid_t                    target_pid                      = -1;
static int                      inherit                         = 1;
static int                      force                           = 0;
static int                      append_file                     = 0;
static int                      call_graph                      = 0;
static int                      verbose                         = 0;

static long                     samples;
static struct timeval           last_read;
static struct timeval           this_read;

static __u64                    bytes_written;

static struct pollfd            event_array[MAX_NR_CPUS * MAX_COUNTERS];

static int                      nr_poll;
static int                      nr_cpu;

struct mmap_event {
        struct perf_event_header        header;
        __u32                           pid;
        __u32                           tid;
        __u64                           start;
        __u64                           len;
        __u64                           pgoff;
        char                            filename[PATH_MAX];
};

struct comm_event {
        struct perf_event_header        header;
        __u32                           pid;
        __u32                           tid;
        char                            comm[16];
};


struct mmap_data {
        int                     counter;
        void                    *base;
        unsigned int            mask;
        unsigned int            prev;
};

static struct mmap_data         mmap_array[MAX_NR_CPUS][MAX_COUNTERS];

static unsigned int mmap_read_head(struct mmap_data *md)
{
        struct perf_counter_mmap_page *pc = md->base;
        int head;

        head = pc->data_head;
        rmb();

        return head;
}

static void mmap_read(struct mmap_data *md)
{
        unsigned int head = mmap_read_head(md);
        unsigned int old = md->prev;
        unsigned char *data = md->base + page_size;
        unsigned long size;
        void *buf;
        int diff;

        gettimeofday(&this_read, NULL);

        /*
         * If we're further behind than half the buffer, there's a chance
         * the writer will bite our tail and mess up the samples under us.
         *
         * If we somehow ended up ahead of the head, we got messed up.
         *
         * In either case, truncate and restart at head.
         */
        diff = head - old;
        if (diff > md->mask / 2 || diff < 0) {
                struct timeval iv;
                unsigned long msecs;

                timersub(&this_read, &last_read, &iv);
                msecs = iv.tv_sec*1000 + iv.tv_usec/1000;

                fprintf(stderr, "WARNING: failed to keep up with mmap data."
                                "  Last read %lu msecs ago.\n", msecs);

                /*
                 * head points to a known good entry, start there.
                 */
                old = head;
        }

        last_read = this_read;

        if (old != head)
                samples++;

        size = head - old;

        if ((old & md->mask) + size != (head & md->mask)) {
                buf = &data[old & md->mask];
                size = md->mask + 1 - (old & md->mask);
                old += size;

                while (size) {
                        int ret = write(output, buf, size);

                        if (ret < 0)
                                die("failed to write");

                        size -= ret;
                        buf += ret;

                        bytes_written += ret;
                }
        }

        buf = &data[old & md->mask];
        size = head - old;
        old += size;

        while (size) {
                int ret = write(output, buf, size);

                if (ret < 0)
                        die("failed to write");

                size -= ret;
                buf += ret;

                bytes_written += ret;
        }

        md->prev = old;
}

static volatile int done = 0;
static volatile int signr = -1;

static void sig_handler(int sig)
{
        done = 1;
        signr = sig;
}

static void sig_atexit(void)
{
        if (signr == -1)
                return;

        signal(signr, SIG_DFL);
        kill(getpid(), signr);
}

static void pid_synthesize_comm_event(pid_t pid, int full)
{
        struct comm_event comm_ev;
        char filename[PATH_MAX];
        char bf[BUFSIZ];
        int fd, ret;
        size_t size;
        char *field, *sep;
        DIR *tasks;
        struct dirent dirent, *next;

        snprintf(filename, sizeof(filename), "/proc/%d/stat", pid);

        fd = open(filename, O_RDONLY);
        if (fd < 0) {
                /*
                 * We raced with a task exiting - just return:
                 */
                if (verbose)
                        fprintf(stderr, "couldn't open %s\n", filename);
                return;
        }
        if (read(fd, bf, sizeof(bf)) < 0) {
                fprintf(stderr, "couldn't read %s\n", filename);
                exit(EXIT_FAILURE);
        }
        close(fd);

        /* 9027 (cat) R 6747 9027 6747 34816 9027 ... */
        memset(&comm_ev, 0, sizeof(comm_ev));
        field = strchr(bf, '(');
        if (field == NULL)
                goto out_failure;
        sep = strchr(++field, ')');
        if (sep == NULL)
                goto out_failure;
        size = sep - field;
        memcpy(comm_ev.comm, field, size++);

        comm_ev.pid = pid;
        comm_ev.header.type = PERF_EVENT_COMM;
        size = ALIGN(size, sizeof(__u64));
        comm_ev.header.size = sizeof(comm_ev) - (sizeof(comm_ev.comm) - size);

        if (!full) {
                comm_ev.tid = pid;

                ret = write(output, &comm_ev, comm_ev.header.size);
                if (ret < 0) {
                        perror("failed to write");
                        exit(-1);
                }
                return;
        }

        snprintf(filename, sizeof(filename), "/proc/%d/task", pid);

        tasks = opendir(filename);
        while (!readdir_r(tasks, &dirent, &next) && next) {
                char *end;
                pid = strtol(dirent.d_name, &end, 10);
                if (*end)
                        continue;

                comm_ev.tid = pid;

                ret = write(output, &comm_ev, comm_ev.header.size);
                if (ret < 0) {
                        perror("failed to write");
                        exit(-1);
                }
        }
        closedir(tasks);
        return;

out_failure:
        fprintf(stderr, "couldn't get COMM and pgid, malformed %s\n",
                filename);
        exit(EXIT_FAILURE);
}

static void pid_synthesize_mmap_samples(pid_t pid)
{
        char filename[PATH_MAX];
        FILE *fp;

        snprintf(filename, sizeof(filename), "/proc/%d/maps", pid);

        fp = fopen(filename, "r");
        if (fp == NULL) {
                /*
                 * We raced with a task exiting - just return:
                 */
                if (verbose)
                        fprintf(stderr, "couldn't open %s\n", filename);
                return;
        }
        while (1) {
                char bf[BUFSIZ], *pbf = bf;
                struct mmap_event mmap_ev = {
                        .header.type = PERF_EVENT_MMAP,
                };
                int n;
                size_t size;
                if (fgets(bf, sizeof(bf), fp) == NULL)
                        break;

                /* 00400000-0040c000 r-xp 00000000 fd:01 41038  /bin/cat */
                n = hex2u64(pbf, &mmap_ev.start);
                if (n < 0)
                        continue;
                pbf += n + 1;
                n = hex2u64(pbf, &mmap_ev.len);
                if (n < 0)
                        continue;
                pbf += n + 3;
                if (*pbf == 'x') { /* vm_exec */
                        char *execname = strrchr(bf, ' ');

                        if (execname == NULL || execname[1] != '/')
                                continue;

                        execname += 1;
                        size = strlen(execname);
                        execname[size - 1] = '\0'; /* Remove \n */
                        memcpy(mmap_ev.filename, execname, size);
                        size = ALIGN(size, sizeof(__u64));
                        mmap_ev.len -= mmap_ev.start;
                        mmap_ev.header.size = (sizeof(mmap_ev) -
                                               (sizeof(mmap_ev.filename) - size));
                        mmap_ev.pid = pid;
                        mmap_ev.tid = pid;

                        if (write(output, &mmap_ev, mmap_ev.header.size) < 0) {
                                perror("failed to write");
                                exit(-1);
                        }
                }
        }

        fclose(fp);
}

static void synthesize_samples(void)
{
        DIR *proc;
        struct dirent dirent, *next;

        proc = opendir("/proc");

        while (!readdir_r(proc, &dirent, &next) && next) {
                char *end;
                pid_t pid;

                pid = strtol(dirent.d_name, &end, 10);
                if (*end) /* only interested in proper numerical dirents */
                        continue;

                pid_synthesize_comm_event(pid, 1);
                pid_synthesize_mmap_samples(pid);
        }

        closedir(proc);
}

static int group_fd;

static void create_counter(int counter, int cpu, pid_t pid)
{
        struct perf_counter_attr *attr = attrs + counter;
        int track = 1;

        attr->sample_type       = PERF_SAMPLE_IP | PERF_SAMPLE_TID;

        if (freq) {
                attr->sample_type       |= PERF_SAMPLE_PERIOD;
                attr->freq              = 1;
                attr->sample_freq       = freq;
        }

        if (call_graph)
                attr->sample_type       |= PERF_SAMPLE_CALLCHAIN;

        attr->mmap              = track;
        attr->comm              = track;
        attr->inherit           = (cpu < 0) && inherit;
        attr->disabled          = 1;

        track = 0; /* only the first counter needs these */

try_again:
        fd[nr_cpu][counter] = sys_perf_counter_open(attr, pid, cpu, group_fd, 0);

        if (fd[nr_cpu][counter] < 0) {
                int err = errno;

                if (err == EPERM)
                        die("Permission error - are you root?\n");

                /*
                 * If it's cycles then fall back to hrtimer
                 * based cpu-clock-tick sw counter, which
                 * is always available even if no PMU support:
                 */
                if (attr->type == PERF_TYPE_HARDWARE
                        && attr->config == PERF_COUNT_HW_CPU_CYCLES) {

                        if (verbose)
                                warning(" ... trying to fall back to cpu-clock-ticks\n");
                        attr->type = PERF_TYPE_SOFTWARE;
                        attr->config = PERF_COUNT_SW_CPU_CLOCK;
                        goto try_again;
                }
                printf("\n");
                error("perfcounter syscall returned with %d (%s)\n",
                        fd[nr_cpu][counter], strerror(err));
                die("No CONFIG_PERF_COUNTERS=y kernel support configured?\n");
                exit(-1);
        }

        assert(fd[nr_cpu][counter] >= 0);
        fcntl(fd[nr_cpu][counter], F_SETFL, O_NONBLOCK);

        /*
         * First counter acts as the group leader:
         */
        if (group && group_fd == -1)
                group_fd = fd[nr_cpu][counter];

        event_array[nr_poll].fd = fd[nr_cpu][counter];
        event_array[nr_poll].events = POLLIN;
        nr_poll++;

        mmap_array[nr_cpu][counter].counter = counter;
        mmap_array[nr_cpu][counter].prev = 0;
        mmap_array[nr_cpu][counter].mask = mmap_pages*page_size - 1;
        mmap_array[nr_cpu][counter].base = mmap(NULL, (mmap_pages+1)*page_size,
                        PROT_READ, MAP_SHARED, fd[nr_cpu][counter], 0);
        if (mmap_array[nr_cpu][counter].base == MAP_FAILED) {
                error("failed to mmap with %d (%s)\n", errno, strerror(errno));
                exit(-1);
        }

        ioctl(fd[nr_cpu][counter], PERF_COUNTER_IOC_ENABLE);
}

static void open_counters(int cpu, pid_t pid)
{
        int counter;

        if (pid > 0) {
                pid_synthesize_comm_event(pid, 0);
                pid_synthesize_mmap_samples(pid);
        }

        group_fd = -1;
        for (counter = 0; counter < nr_counters; counter++)
                create_counter(counter, cpu, pid);

        nr_cpu++;
}

static int __cmd_record(int argc, const char **argv)
{
        int i, counter;
        struct stat st;
        pid_t pid;
        int flags;
        int ret;

        page_size = sysconf(_SC_PAGE_SIZE);
        nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
        assert(nr_cpus <= MAX_NR_CPUS);
        assert(nr_cpus >= 0);

        if (!stat(output_name, &st) && !force && !append_file) {
                fprintf(stderr, "Error, output file %s exists, use -A to append or -f to overwrite.\n",
                                output_name);
                exit(-1);
        }

        flags = O_CREAT|O_RDWR;
        if (append_file)
                flags |= O_APPEND;
        else
                flags |= O_TRUNC;

        output = open(output_name, flags, S_IRUSR|S_IWUSR);
        if (output < 0) {
                perror("failed to create output file");
                exit(-1);
        }

        if (!system_wide) {
                open_counters(-1, target_pid != -1 ? target_pid : getpid());
        } else for (i = 0; i < nr_cpus; i++)
                open_counters(i, target_pid);

        atexit(sig_atexit);
        signal(SIGCHLD, sig_handler);
        signal(SIGINT, sig_handler);

        if (target_pid == -1 && argc) {
                pid = fork();
                if (pid < 0)
                        perror("failed to fork");

                if (!pid) {
                        if (execvp(argv[0], (char **)argv)) {
                                perror(argv[0]);
                                exit(-1);
                        }
                }
        }

        if (realtime_prio) {
                struct sched_param param;

                param.sched_priority = realtime_prio;
                if (sched_setscheduler(0, SCHED_FIFO, &param)) {
                        printf("Could not set realtime priority.\n");
                        exit(-1);
                }
        }

        if (system_wide)
                synthesize_samples();

        while (!done) {
                int hits = samples;

                for (i = 0; i < nr_cpu; i++) {
                        for (counter = 0; counter < nr_counters; counter++)
                                mmap_read(&mmap_array[i][counter]);
                }

                if (hits == samples)
                        ret = poll(event_array, nr_poll, 100);
        }

        /*
         * Approximate RIP event size: 24 bytes.
         */
        fprintf(stderr,
                "[ perf record: Captured and wrote %.3f MB %s (~%lld samples) ]\n",
                (double)bytes_written / 1024.0 / 1024.0,
                output_name,
                bytes_written / 24);

        return 0;
}

static const char * const record_usage[] = {
        "perf record [<options>] [<command>]",
        "perf record [<options>] -- <command> [<options>]",
        NULL
};

static const struct option options[] = {
        OPT_CALLBACK('e', "event", NULL, "event",
                     "event selector. use 'perf list' to list available events",
                     parse_events),
        OPT_INTEGER('p', "pid", &target_pid,
                    "record events on existing pid"),
        OPT_INTEGER('r', "realtime", &realtime_prio,
                    "collect data with this RT SCHED_FIFO priority"),
        OPT_BOOLEAN('a', "all-cpus", &system_wide,
                            "system-wide collection from all CPUs"),
        OPT_BOOLEAN('A', "append", &append_file,
                            "append to the output file to do incremental profiling"),
        OPT_BOOLEAN('f', "force", &force,
                        "overwrite existing data file"),
        OPT_LONG('c', "count", &default_interval,
                    "event period to sample"),
        OPT_STRING('o', "output", &output_name, "file",
                    "output file name"),
        OPT_BOOLEAN('i', "inherit", &inherit,
                    "child tasks inherit counters"),
        OPT_INTEGER('F', "freq", &freq,
                    "profile at this frequency"),
        OPT_INTEGER('m', "mmap-pages", &mmap_pages,
                    "number of mmap data pages"),
        OPT_BOOLEAN('g', "call-graph", &call_graph,
                    "do call-graph (stack chain/backtrace) recording"),
        OPT_BOOLEAN('v', "verbose", &verbose,
                    "be more verbose (show counter open errors, etc)"),
        OPT_END()
};

int cmd_record(int argc, const char **argv, const char *prefix)
{
        int counter;

        argc = parse_options(argc, argv, options, record_usage, 0);
        if (!argc && target_pid == -1 && !system_wide)
                usage_with_options(record_usage, options);

        if (!nr_counters) {
                nr_counters     = 1;
                attrs[0].type   = PERF_TYPE_HARDWARE;
                attrs[0].config = PERF_COUNT_HW_CPU_CYCLES;
        }

        for (counter = 0; counter < nr_counters; counter++) {
                if (attrs[counter].sample_period)
                        continue;

                attrs[counter].sample_period = default_interval;
        }

        return __cmd_record(argc, argv);
}