From 52a552e21ae25eb175f686935fe85a2956f949ce Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Fri, 3 Jan 2020 11:35:22 -0800 Subject: [PATCH] Fix a potential deadlock in helper_do_stat() pthread_mutex_lock(), pthread_cond_signal() and pthread_mutex_unlock() are not async-signal-safe and hence must not be used inside a singal handler implementation. Rework the code for communication with the helper thread such that it becomes async-signal-safe. Compared to commit 31eca641ad91, tests for the pipe() and pipe2() system calls have been added and a pipe simulation for Windows has been added (pipe_over_localhost()). Fixes: a47591e4923f ("Improve logging accuracy") Signed-off-by: Bart Van Assche --- configure | 42 +++++++++++ helper_thread.c | 191 ++++++++++++++++++++++++++++++++++++++---------- 2 files changed, 194 insertions(+), 39 deletions(-) diff --git a/configure b/configure index 3a675a46..2671c325 100755 --- a/configure +++ b/configure @@ -1113,6 +1113,42 @@ if compile_prog "" "" "fdatasync"; then fi print_config "fdatasync" "$fdatasync" +########################################## +# pipe() probe +if test "$pipe" != "yes" ; then + pipe="no" +fi +cat > $TMPC << EOF +#include +int main(int argc, char **argv) +{ + int fd[2]; + return pipe(fd); +} +EOF +if compile_prog "" "" "pipe"; then + pipe="yes" +fi +print_config "pipe()" "$pipe" + +########################################## +# pipe2() probe +if test "$pipe2" != "yes" ; then + pipe2="no" +fi +cat > $TMPC << EOF +#include +int main(int argc, char **argv) +{ + int fd[2]; + return pipe2(fd, 0); +} +EOF +if compile_prog "" "" "pipe2"; then + pipe2="yes" +fi +print_config "pipe2()" "$pipe2" + ########################################## # pread() probe if test "$pread" != "yes" ; then @@ -2513,6 +2549,12 @@ fi if test "$fdatasync" = "yes" ; then output_sym "CONFIG_FDATASYNC" fi +if test "$pipe" = "yes" ; then + output_sym "CONFIG_PIPE" +fi +if test "$pipe2" = "yes" ; then + output_sym "CONFIG_PIPE2" +fi if test "$pread" = "yes" ; then output_sym "CONFIG_PREAD" fi diff --git a/helper_thread.c b/helper_thread.c index 51e8f06f..28f6cca3 100644 --- a/helper_thread.c +++ b/helper_thread.c @@ -10,14 +10,17 @@ #include "steadystate.h" #include "pshared.h" +enum action { + A_EXIT = 1, + A_RESET = 2, + A_DO_STAT = 3, +}; + static struct helper_data { volatile int exit; - volatile int reset; - volatile int do_stat; + int pipe[2]; /* 0: read end; 1: write end. */ struct sk_out *sk_out; pthread_t thread; - pthread_mutex_t lock; - pthread_cond_t cond; struct fio_sem *startup_sem; } *helper_data; @@ -26,35 +29,84 @@ void helper_thread_destroy(void) if (!helper_data) return; - pthread_cond_destroy(&helper_data->cond); - pthread_mutex_destroy(&helper_data->lock); + close(helper_data->pipe[0]); + close(helper_data->pipe[1]); sfree(helper_data); } -void helper_reset(void) +#ifdef _WIN32 +static void sock_init(void) { - if (!helper_data) - return; + WSADATA wsaData; + int res; - pthread_mutex_lock(&helper_data->lock); + /* It is allowed to call WSAStartup() more than once. */ + res = WSAStartup(MAKEWORD(2, 2), &wsaData); + assert(res == 0); +} - if (!helper_data->reset) { - helper_data->reset = 1; - pthread_cond_signal(&helper_data->cond); - } +static int make_nonblocking(int fd) +{ + unsigned long arg = 1; - pthread_mutex_unlock(&helper_data->lock); + return ioctlsocket(fd, FIONBIO, &arg); } -void helper_do_stat(void) +static int write_to_pipe(int fd, const void *buf, size_t len) +{ + return send(fd, buf, len, 0); +} + +static int read_from_pipe(int fd, void *buf, size_t len) +{ + return recv(fd, buf, len, 0); +} +#else +static void sock_init(void) +{ +} + +static int make_nonblocking(int fd) +{ + return fcntl(fd, F_SETFL, O_NONBLOCK); +} + +static int write_to_pipe(int fd, const void *buf, size_t len) +{ + return write(fd, buf, len); +} + +static int read_from_pipe(int fd, void *buf, size_t len) +{ + return read(fd, buf, len); +} +#endif + +static void submit_action(enum action a) { + const char data = a; + int ret; + if (!helper_data) return; - pthread_mutex_lock(&helper_data->lock); - helper_data->do_stat = 1; - pthread_cond_signal(&helper_data->cond); - pthread_mutex_unlock(&helper_data->lock); + ret = write_to_pipe(helper_data->pipe[1], &data, sizeof(data)); + assert(ret == 1); +} + +void helper_reset(void) +{ + submit_action(A_RESET); +} + +/* + * May be invoked in signal handler context and hence must only call functions + * that are async-signal-safe. See also + * https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03. + */ +void helper_do_stat(void) +{ + submit_action(A_DO_STAT); } bool helper_should_exit(void) @@ -67,17 +119,12 @@ bool helper_should_exit(void) void helper_thread_exit(void) { - void *ret; - if (!helper_data) return; - pthread_mutex_lock(&helper_data->lock); helper_data->exit = 1; - pthread_cond_signal(&helper_data->cond); - pthread_mutex_unlock(&helper_data->lock); - - pthread_join(helper_data->thread, &ret); + submit_action(A_EXIT); + pthread_join(helper_data->thread, NULL); } static void *helper_thread_main(void *data) @@ -85,6 +132,7 @@ static void *helper_thread_main(void *data) struct helper_data *hd = data; unsigned int msec_to_next_event, next_log, next_ss = STEADYSTATE_MSEC; struct timespec ts, last_du, last_ss; + char action; int ret = 0; sk_out_assign(hd->sk_out); @@ -102,11 +150,24 @@ static void *helper_thread_main(void *data) msec_to_next_event = DISK_UTIL_MSEC; while (!ret && !hd->exit) { uint64_t since_du, since_ss = 0; + struct timeval timeout = { + .tv_sec = DISK_UTIL_MSEC / 1000, + .tv_usec = (DISK_UTIL_MSEC % 1000) * 1000, + }; + fd_set rfds, efds; timespec_add_msec(&ts, msec_to_next_event); - pthread_mutex_lock(&hd->lock); - pthread_cond_timedwait(&hd->cond, &hd->lock, &ts); + if (read_from_pipe(hd->pipe[0], &action, sizeof(action)) < 0) { + FD_ZERO(&rfds); + FD_SET(hd->pipe[0], &rfds); + FD_ZERO(&efds); + FD_SET(hd->pipe[0], &efds); + select(1, &rfds, NULL, &efds, &timeout); + if (read_from_pipe(hd->pipe[0], &action, sizeof(action)) < + 0) + action = 0; + } #ifdef CONFIG_PTHREAD_CONDATTR_SETCLOCK clock_gettime(CLOCK_MONOTONIC, &ts); @@ -114,14 +175,11 @@ static void *helper_thread_main(void *data) clock_gettime(CLOCK_REALTIME, &ts); #endif - if (hd->reset) { - memcpy(&last_du, &ts, sizeof(ts)); - memcpy(&last_ss, &ts, sizeof(ts)); - hd->reset = 0; + if (action == A_RESET) { + last_du = ts; + last_ss = ts; } - pthread_mutex_unlock(&hd->lock); - since_du = mtime_since(&last_du, &ts); if (since_du >= DISK_UTIL_MSEC || DISK_UTIL_MSEC - since_du < 10) { ret = update_io_ticks(); @@ -132,10 +190,8 @@ static void *helper_thread_main(void *data) } else msec_to_next_event = DISK_UTIL_MSEC - since_du; - if (hd->do_stat) { - hd->do_stat = 0; + if (action == A_DO_STAT) __show_running_run_stats(); - } next_log = calc_log_samples(); if (!next_log) @@ -167,6 +223,54 @@ static void *helper_thread_main(void *data) return NULL; } +/* + * Connect two sockets to each other to emulate the pipe() system call on Windows. + */ +int pipe_over_loopback(int fd[2]) +{ + struct sockaddr_in addr = { .sin_family = AF_INET }; + socklen_t len = sizeof(addr); + int res; + + addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK); + + sock_init(); + + fd[0] = socket(AF_INET, SOCK_STREAM, 0); + if (fd[0] < 0) + goto err; + fd[1] = socket(AF_INET, SOCK_STREAM, 0); + if (fd[1] < 0) + goto close_fd_0; + res = bind(fd[0], (struct sockaddr *)&addr, len); + if (res < 0) + goto close_fd_1; + res = getsockname(fd[0], (struct sockaddr *)&addr, &len); + if (res < 0) + goto close_fd_1; + res = listen(fd[0], 1); + if (res < 0) + goto close_fd_1; + res = connect(fd[1], (struct sockaddr *)&addr, len); + if (res < 0) + goto close_fd_1; + res = accept(fd[0], NULL, NULL); + if (res < 0) + goto close_fd_1; + close(fd[0]); + fd[0] = res; + return 0; + +close_fd_1: + close(fd[1]); + +close_fd_0: + close(fd[0]); + +err: + return -1; +} + int helper_thread_create(struct fio_sem *startup_sem, struct sk_out *sk_out) { struct helper_data *hd; @@ -179,10 +283,19 @@ int helper_thread_create(struct fio_sem *startup_sem, struct sk_out *sk_out) hd->sk_out = sk_out; - ret = mutex_cond_init_pshared(&hd->lock, &hd->cond); +#if defined(CONFIG_PIPE2) + ret = pipe2(hd->pipe, O_CLOEXEC); +#elif defined(CONFIG_PIPE) + ret = pipe(hd->pipe); +#else + ret = pipe_over_loopback(hd->pipe); +#endif if (ret) return 1; + ret = make_nonblocking(hd->pipe[0]); + assert(ret >= 0); + hd->startup_sem = startup_sem; DRD_IGNORE_VAR(helper_data); -- 2.25.1