From 7455e05e4e750451eb3c33359a2bc9050156750c Mon Sep 17 00:00:00 2001 From: Jeff Hostetler Date: Mon, 15 Mar 2021 21:08:18 +0000 Subject: pkt-line: eliminate the need for static buffer in packet_write_gently() Teach `packet_write_gently()` to write the pkt-line header and the actual buffer in 2 separate calls to `write_in_full()` and avoid the need for a static buffer, thread-safe scratch space, or an excessively large stack buffer. Change `write_packetized_from_fd()` to allocate a temporary buffer rather than using a static buffer to avoid similar issues here. These changes are intended to make it easier to use pkt-line routines in a multi-threaded context with multiple concurrent writers writing to different streams. Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano --- pkt-line.c | 28 ++++++++++++++++++++-------- 1 file changed, 20 insertions(+), 8 deletions(-) (limited to 'pkt-line.c') diff --git a/pkt-line.c b/pkt-line.c index d633005ef7..66bd0ddfd1 100644 --- a/pkt-line.c +++ b/pkt-line.c @@ -196,17 +196,26 @@ int packet_write_fmt_gently(int fd, const char *fmt, ...) static int packet_write_gently(const int fd_out, const char *buf, size_t size) { - static char packet_write_buffer[LARGE_PACKET_MAX]; + char header[4]; size_t packet_size; - if (size > sizeof(packet_write_buffer) - 4) + if (size > LARGE_PACKET_DATA_MAX) return error(_("packet write failed - data exceeds max packet size")); packet_trace(buf, size, 1); packet_size = size + 4; - set_packet_header(packet_write_buffer, packet_size); - memcpy(packet_write_buffer + 4, buf, size); - if (write_in_full(fd_out, packet_write_buffer, packet_size) < 0) + + set_packet_header(header, packet_size); + + /* + * Write the header and the buffer in 2 parts so that we do + * not need to allocate a buffer or rely on a static buffer. + * This also avoids putting a large buffer on the stack which + * might have multi-threading issues. + */ + + if (write_in_full(fd_out, header, 4) < 0 || + write_in_full(fd_out, buf, size) < 0) return error(_("packet write failed")); return 0; } @@ -244,20 +253,23 @@ void packet_buf_write_len(struct strbuf *buf, const char *data, size_t len) int write_packetized_from_fd(int fd_in, int fd_out) { - static char buf[LARGE_PACKET_DATA_MAX]; + char *buf = xmalloc(LARGE_PACKET_DATA_MAX); int err = 0; ssize_t bytes_to_write; while (!err) { - bytes_to_write = xread(fd_in, buf, sizeof(buf)); - if (bytes_to_write < 0) + bytes_to_write = xread(fd_in, buf, LARGE_PACKET_DATA_MAX); + if (bytes_to_write < 0) { + free(buf); return COPY_READ_ERROR; + } if (bytes_to_write == 0) break; err = packet_write_gently(fd_out, buf, bytes_to_write); } if (!err) err = packet_flush_gently(fd_out); + free(buf); return err; } -- cgit v1.2.3