Messages in this thread | | | Date | Tue, 15 Jul 2014 15:46:12 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] ring-buffer: Fix polling on trace_pipe |
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On Thu, 10 Jul 2014 15:20:30 -0700 Martin Lau <kafai@fb.com> wrote:
> Hi Steve, > > Do you have a chance to give it another try? >
OK, I finally got around to testing it. Yep I see your point. Do you think it should go to 3.16 and stable? I can add it to my next git pull request.
Also, I modified your test such that it wouldn't hang on failure, but detects that it hung and returns a exit value to add this to my testing. That is, it exits with zero on success and non zero on failure.
-- Steve #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/wait.h> #include <sys/stat.h> #include <sys/epoll.h> #include <fcntl.h> #include <unistd.h> #include <assert.h> #include <signal.h> #include <errno.h>
static const char * debugfs_list[] = { "/debug/tracing", "/sys/kernel/debug/tracing", "/d/tracing", NULL, };
static const char *debugfs; static int markfd; static int trace_pipe_fd;
static void alog(const char *name, int ret) { printf("%d: %s: %d\n", getpid(), name, ret); }
static const char *find_debugfs(void) { struct stat st; int i; int r;
for (i = 0; debugfs_list[i]; i++) { r = stat(debugfs_list[i], &st); if (r < 0) continue; if (S_ISDIR(st.st_mode)) return debugfs_list[i]; } return NULL; }
static char * make_path(const char *file) { char *path; int size;
size = strlen(debugfs) + strlen(file) + 2; path = malloc(size); if (!path) { perror("malloc"); exit(-1); } sprintf(path, "%s/%s", debugfs, file); return path; }
static void mark_write(const char *str) { int ret; ret = write(markfd, str, strlen(str)); alog("write(markfd)", ret); }
static void read_trace_pipe(void) { char buf[1024]; int r;
while ((r = read(trace_pipe_fd, buf, 1024)) > 0) printf("%.*s", r, buf); }
int main (int argc, char **argv) { struct epoll_event ee; char *marker; char *pipe; int efd; int ret; pid_t dwrt_pid;
debugfs = find_debugfs(); if (!debugfs) { fprintf(stderr, "Could not find debugfs\n"); exit(-1); }
marker = make_path("trace_marker"); pipe = make_path("trace_pipe");
markfd = open(marker, O_WRONLY); if (markfd < 0) { perror("marker"); exit(-1); } trace_pipe_fd = open(pipe, O_RDONLY|O_NONBLOCK); if (trace_pipe_fd < 0) { perror("trace_pipe"); exit(-1); }
efd = epoll_create(1); if (efd < 0) { perror("epoll_create"); exit(-1); }
mark_write("some data"); memset(&ee, 0, sizeof(ee)); ee.events = EPOLLIN; ret = epoll_ctl(efd, EPOLL_CTL_ADD, trace_pipe_fd, &ee); if (ret < 0) { perror("epoll_ctl"); exit(-1); } alog("waiting data......", 0); ret = epoll_wait(efd, &ee, 1, -1); alog("epoll_wait()", ret); read_trace_pipe(); dwrt_pid = fork(); assert(dwrt_pid != -1); if (dwrt_pid > 0) { int status; sleep(10); mark_write("more data"); sleep(10); ret = waitpid(dwrt_pid, &status, WNOHANG); if (ret != dwrt_pid) { alog("Poll never finished!", 0); kill(dwrt_pid, 9); exit(-1); } if (WEXITSTATUS(status) != 0) { alog("Something failed on polling!", WEXITSTATUS(status)); exit(-1); } } else { alog("waiting form more data......", 0); ret = epoll_wait(efd, &ee, 1, -1); alog("epoll_wait()", ret); read_trace_pipe(); if (ret < 0) exit(errno); } exit (0); }
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