The read/write loop in save_trace_to_file() does not correctly handle errors from the read() and write() system calls. If either call is interrupted by a signal, it returns -1 with errno set to EINTR, but the code treats this as a fatal error and aborts the save operation. Additionally, write() may perform a partial write, returning fewer bytes than requested, which the code does not handle.
Fix the I/O loop by introducing proper error handling. The return value of read() is now stored in a ssize_t variable and checked for errors, with EINTR causing a retry. For write(), an inner loop ensures all bytes are written, handling both EINTR and partial writes. Error messages now include strerror() output for better debugging. This follows the same pattern established in the previous commit that fixed trace_event_save_hist(), ensuring consistent and robust I/O handling throughout the trace saving code. Signed-off-by: Wander Lairson Costa <[email protected]> --- tools/tracing/rtla/src/trace.c | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) diff --git a/tools/tracing/rtla/src/trace.c b/tools/tracing/rtla/src/trace.c index fed3362527b08..8e93b48d33ef8 100644 --- a/tools/tracing/rtla/src/trace.c +++ b/tools/tracing/rtla/src/trace.c @@ -73,6 +73,7 @@ int save_trace_to_file(struct tracefs_instance *inst, const char *filename) char buffer[4096]; int out_fd, in_fd; int retval = -1; + ssize_t n_read; if (!inst || !filename) return 0; @@ -90,15 +91,30 @@ int save_trace_to_file(struct tracefs_instance *inst, const char *filename) goto out_close_in; } - do { - retval = read(in_fd, buffer, sizeof(buffer)); - if (retval <= 0) + for (;;) { + n_read = read(in_fd, buffer, sizeof(buffer)); + if (n_read < 0) { + if (errno == EINTR) + continue; + err_msg("Error reading trace file: %s\n", strerror(errno)); goto out_close; + } + if (n_read == 0) + break; - retval = write(out_fd, buffer, retval); - if (retval < 0) - goto out_close; - } while (retval > 0); + ssize_t n_written = 0; + while (n_written < n_read) { + ssize_t w = write(out_fd, buffer + n_written, n_read - n_written); + + if (w < 0) { + if (errno == EINTR) + continue; + err_msg("Error writing trace file: %s\n", strerror(errno)); + goto out_close; + } + n_written += w; + } + } retval = 0; out_close: -- 2.52.0
