diff options
| -rw-r--r-- | Documentation/ftrace.txt | 79 | ||||
| -rw-r--r-- | kernel/trace/ftrace.c | 209 |
2 files changed, 262 insertions, 26 deletions
diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt index 35a78bc6651d..de05042f11b9 100644 --- a/Documentation/ftrace.txt +++ b/Documentation/ftrace.txt @@ -127,6 +127,8 @@ of ftrace. Here is a list of some of the key files: be traced. If a function exists in both set_ftrace_filter and set_ftrace_notrace, the function will _not_ be traced. + set_ftrace_pid: Have the function tracer only trace a single thread. + available_filter_functions: This lists the functions that ftrace has processed and can trace. These are the function names that you can pass to "set_ftrace_filter" or @@ -1073,6 +1075,83 @@ For simple one time traces, the above is sufficent. For anything else, a search through /proc/mounts may be needed to find where the debugfs file-system is mounted. + +Single thread tracing +--------------------- + +By writing into /debug/tracing/set_ftrace_pid you can trace a +single thread. For example: + +# cat /debug/tracing/set_ftrace_pid +no pid +# echo 3111 > /debug/tracing/set_ftrace_pid +# cat /debug/tracing/set_ftrace_pid +3111 +# echo function > /debug/tracing/current_tracer +# cat /debug/tracing/trace | head + # tracer: function + # + # TASK-PID CPU# TIMESTAMP FUNCTION + # | | | | | + yum-updatesd-3111 [003] 1637.254676: finish_task_switch <-thread_return + yum-updatesd-3111 [003] 1637.254681: hrtimer_cancel <-schedule_hrtimeout_range + yum-updatesd-3111 [003] 1637.254682: hrtimer_try_to_cancel <-hrtimer_cancel + yum-updatesd-3111 [003] 1637.254683: lock_hrtimer_base <-hrtimer_try_to_cancel + yum-updatesd-3111 [003] 1637.254685: fget_light <-do_sys_poll + yum-updatesd-3111 [003] 1637.254686: pipe_poll <-do_sys_poll +# echo -1 > /debug/tracing/set_ftrace_pid +# cat /debug/tracing/trace |head + # tracer: function + # + # TASK-PID CPU# TIMESTAMP FUNCTION + # | | | | | + ##### CPU 3 buffer started #### + yum-updatesd-3111 [003] 1701.957688: free_poll_entry <-poll_freewait + yum-updatesd-3111 [003] 1701.957689: remove_wait_queue <-free_poll_entry + yum-updatesd-3111 [003] 1701.957691: fput <-free_poll_entry + yum-updatesd-3111 [003] 1701.957692: audit_syscall_exit <-sysret_audit + yum-updatesd-3111 [003] 1701.957693: path_put <-audit_syscall_exit + +If you want to trace a function when executing, you could use +something like this simple program: + +#include <stdio.h> +#include <stdlib.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <unistd.h> + +int main (int argc, char **argv) +{ + if (argc < 1) + exit(-1); + + if (fork() > 0) { + int fd, ffd; + char line[64]; + int s; + + ffd = open("/debug/tracing/current_tracer", O_WRONLY); + if (ffd < 0) + exit(-1); + write(ffd, "nop", 3); + + fd = open("/debug/tracing/set_ftrace_pid", O_WRONLY); + s = sprintf(line, "%d\n", getpid()); + write(fd, line, s); + + write(ffd, "function", 8); + + close(fd); + close(ffd); + + execvp(argv[1], argv+1); + } + + return 0; +} + dynamic ftrace -------------- diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 7e2d3b91692d..00d98c65fad0 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -47,6 +47,9 @@ int ftrace_enabled __read_mostly; static int last_ftrace_enabled; +/* ftrace_pid_trace >= 0 will only trace threads with this pid */ +static int ftrace_pid_trace = -1; + /* Quick disabling of function tracer. */ int function_trace_stop; @@ -61,6 +64,7 @@ static int ftrace_disabled __read_mostly; static DEFINE_SPINLOCK(ftrace_lock); static DEFINE_MUTEX(ftrace_sysctl_lock); +static DEFINE_MUTEX(ftrace_start_lock); static struct ftrace_ops ftrace_list_end __read_mostly = { @@ -70,6 +74,7 @@ static struct ftrace_ops ftrace_list_end __read_mostly = static struct ftrace_ops *ftrace_list __read_mostly = &ftrace_list_end; ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub; ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub; +ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub; static void ftrace_list_func(unsigned long ip, unsigned long parent_ip) { @@ -86,6 +91,21 @@ static void ftrace_list_func(unsigned long ip, unsigned long parent_ip) }; } +static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip) +{ + if (current->pid != ftrace_pid_trace) + return; + + ftrace_pid_function(ip, parent_ip); +} + +static void set_ftrace_pid_function(ftrace_func_t func) +{ + /* do not set ftrace_pid_function to itself! */ + if (func != ftrace_pid_func) + ftrace_pid_function = func; +} + /** * clear_ftrace_function - reset the ftrace function * @@ -96,6 +116,7 @@ void clear_ftrace_function(void) { ftrace_trace_function = ftrace_stub; __ftrace_trace_function = ftrace_stub; + ftrace_pid_function = ftrace_stub; } #ifndef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST @@ -128,20 +149,26 @@ static int __register_ftrace_function(struct ftrace_ops *ops) ftrace_list = ops; if (ftrace_enabled) { + ftrace_func_t func; + + if (ops->next == &ftrace_list_end) + func = ops->func; + else + func = ftrace_list_func; + + if (ftrace_pid_trace >= 0) { + set_ftrace_pid_function(func); + func = ftrace_pid_func; + } + /* * For one func, simply call it directly. * For more than one func, call the chain. */ #ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST - if (ops->next == &ftrace_list_end) - ftrace_trace_function = ops->func; - else - ftrace_trace_function = ftrace_list_func; + ftrace_trace_function = func; #else - if (ops->next == &ftrace_list_end) - __ftrace_trace_function = ops->func; - else - __ftrace_trace_function = ftrace_list_func; + __ftrace_trace_function = func; ftrace_trace_function = ftrace_test_stop_func; #endif } @@ -182,8 +209,19 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops) if (ftrace_enabled) { /* If we only have one func left, then call that directly */ - if (ftrace_list->next == &ftrace_list_end) - ftrace_trace_function = ftrace_list->func; + if (ftrace_list->next == &ftrace_list_end) { + ftrace_func_t func = ftrace_list->func; + + if (ftrace_pid_trace >= 0) { + set_ftrace_pid_function(func); + func = ftrace_pid_func; + } +#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST + ftrace_trace_function = func; +#else + __ftrace_trace_function = func; +#endif + } } out: @@ -192,6 +230,38 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops) return ret; } +static void ftrace_update_pid_func(void) +{ + ftrace_func_t func; + + /* should not be called from interrupt context */ + spin_lock(&ftrace_lock); + + if (ftrace_trace_function == ftrace_stub) + goto out; + + func = ftrace_trace_function; + + if (ftrace_pid_trace >= 0) { + set_ftrace_pid_function(func); + func = ftrace_pid_func; + } else { + if (func != ftrace_pid_func) + goto out; + + set_ftrace_pid_function(func); + } + +#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST + ftrace_trace_function = func; +#else + __ftrace_trace_function = func; +#endif + + out: + spin_unlock(&ftrace_lock); +} + #ifdef CONFIG_DYNAMIC_FTRACE #ifndef CONFIG_FTRACE_MCOUNT_RECORD # error Dynamic ftrace depends on MCOUNT_RECORD @@ -545,7 +615,19 @@ static void ftrace_run_update_code(int command) static ftrace_func_t saved_ftrace_func; static int ftrace_start_up; -static DEFINE_MUTEX(ftrace_start_lock); + +static void ftrace_startup_enable(int command) +{ + if (saved_ftrace_func != ftrace_trace_function) { + saved_ftrace_func = ftrace_trace_function; + command |= FTRACE_UPDATE_TRACE_FUNC; + } + + if (!command || !ftrace_enabled) + return; + + ftrace_run_update_code(command); +} static void ftrace_startup(void) { @@ -558,16 +640,8 @@ static void ftrace_startup(void) ftrace_start_up++; command |= FTRACE_ENABLE_CALLS; - if (saved_ftrace_func != ftrace_trace_function) { - saved_ftrace_func = ftrace_trace_function; - command |= FTRACE_UPDATE_TRACE_FUNC; - } - - if (!command || !ftrace_enabled) - goto out; + ftrace_startup_enable(command); - ftrace_run_update_code(command); - out: mutex_unlock(&ftrace_start_lock); } @@ -1262,13 +1336,10 @@ static struct file_operations ftrace_notrace_fops = { .release = ftrace_notrace_release, }; -static __init int ftrace_init_debugfs(void) +static __init int ftrace_init_dyn_debugfs(struct dentry *d_tracer) { - struct dentry *d_tracer; struct dentry *entry; - d_tracer = tracing_init_dentry(); - entry = debugfs_create_file("available_filter_functions", 0444, d_tracer, NULL, &ftrace_avail_fops); if (!entry) @@ -1295,8 +1366,6 @@ static __init int ftrace_init_debugfs(void) return 0; } -fs_initcall(ftrace_init_debugfs); - static int ftrace_convert_nops(struct module *mod, unsigned long *start, unsigned long *end) @@ -1382,12 +1451,100 @@ static int __init ftrace_nodyn_init(void) } device_initcall(ftrace_nodyn_init); +static inline int ftrace_init_dyn_debugfs(struct dentry *d_tracer) { return 0; } +static inline void ftrace_startup_enable(int command) { } # define ftrace_startup() do { } while (0) # define ftrace_shutdown() do { } while (0) # define ftrace_startup_sysctl() do { } while (0) # define ftrace_shutdown_sysctl() do { } while (0) #endif /* CONFIG_DYNAMIC_FTRACE */ +static ssize_t +ftrace_pid_read(struct file *file, char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + char buf[64]; + int r; + + if (ftrace_pid_trace >= 0) + r = sprintf(buf, "%u\n", ftrace_pid_trace); + else + r = sprintf(buf, "no pid\n"); + + return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); +} + +static ssize_t +ftrace_pid_write(struct file *filp, const char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + char buf[64]; + long val; + int ret; + + if (cnt >= sizeof(buf)) + return -EINVAL; + + if (copy_from_user(&buf, ubuf, cnt)) + return -EFAULT; + + buf[cnt] = 0; + + ret = strict_strtol(buf, 10, &val); + if (ret < 0) + return ret; + + mutex_lock(&ftrace_start_lock); + if (ret < 0) { + /* disable pid tracing */ + if (ftrace_pid_trace < 0) + goto out; + ftrace_pid_trace = -1; + + } else { + + if (ftrace_pid_trace == val) + goto out; + + ftrace_pid_trace = val; + } + + /* update the function call */ + ftrace_update_pid_func(); + ftrace_startup_enable(0); + + out: + mutex_unlock(&ftrace_start_lock); + + return cnt; +} + +static struct file_operations ftrace_pid_fops = { + .read = ftrace_pid_read, + .write = ftrace_pid_write, +}; + +static __init int ftrace_init_debugfs(void) +{ + struct dentry *d_tracer; + struct dentry *entry; + + d_tracer = tracing_init_dentry(); + if (!d_tracer) + return 0; + + ftrace_init_dyn_debugfs(d_tracer); + + entry = debugfs_create_file("set_ftrace_pid", 0644, d_tracer, + NULL, &ftrace_pid_fops); + if (!entry) + pr_warning("Could not create debugfs " + "'set_ftrace_pid' entry\n"); + return 0; +} + +fs_initcall(ftrace_init_debugfs); + /** * ftrace_kill - kill ftrace * |