Commit 47dd74f6 authored by Wander Lairson Costa's avatar Wander Lairson Costa Committed by Tomas Glozar
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rtla/trace: Fix I/O handling in save_trace_to_file() 



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: default avatarWander Lairson Costa <wander@redhat.com>
Link: https://lore.kernel.org/r/20260309195040.1019085-17-wander@redhat.com


Signed-off-by: default avatarTomas Glozar <tglozar@redhat.com>
parent 4bf4ef52

tools/tracing/rtla/src/trace.c

+24 −7
Original line number Diff line number Diff line
@@ -73,6 +73,8 @@ 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;

	ssize_t n_written;



	if (!inst || !filename)

		return 0;
@@ -90,15 +92,30 @@ 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)

		n_written = 0;

		while (n_written < n_read) {

			const 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;

	} while (retval > 0);

			}

			n_written += w;

		}

	}



	retval = 0;

out_close: