Commit 7983e829 authored Sep 06, 2016 by Daniel P. Berrangé Committed by Paolo Bonzini Sep 13, 2016

sclpconsolelm: remove bogus check for -EAGAIN



The write_console_data() method in sclpconsole-lm.c checks
whether the return value of qemu_chr_fe_write() has the
value of -EAGAIN and if so then increments the buffer offset
by the value of EAGAIN. Fortunately qemu_chr_fe_write() will
never return EAGAIN directly, rather it returns -1 with
errno set to EAGAIN, so this broken code path was not
reachable. The behaviour on EAGAIN was stil bad though,
causing the write_console_data() to busy_wait repeatedly
calling qemu_chr_fe_write() with no sleep between iters.

Just remove all this loop logic and replace with a call
to qemu_chr_fe_write_all().

Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1473170165-540-3-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent b72981b9

hw/char/sclpconsole-lm.c

+3 −18

Original line number	Diff line number	Diff line
		@@ -191,9 +191,6 @@ static int read_event_data(SCLPEvent event, EventBufferHeader evt_buf_hdr,
		*/
		static int write_console_data(SCLPEvent event, const uint8_t buf, int len)
		{
		int ret = 0;
		const uint8_t *buf_offset;

		SCLPConsoleLM *scon = SCLPLM_CONSOLE(event);

		if (!scon->chr) {
		@@ -201,21 +198,9 @@ static int write_console_data(SCLPEvent event, const uint8_t buf, int len)
		return len;
		}

		buf_offset = buf;
		while (len > 0) {
		ret = qemu_chr_fe_write(scon->chr, buf, len);
		if (ret == 0) {
		/* a pty doesn't seem to be connected - no error */
		len = 0;
		} else if (ret == -EAGAIN \|\| (ret > 0 && ret < len)) {
		len -= ret;
		buf_offset += ret;
		} else {
		len = 0;
		}
		}

		return ret;
		/* XXX this blocks entire thread. Rewrite to use
		* qemu_chr_fe_write and background I/O callbacks */
		return qemu_chr_fe_write_all(scon->chr, buf, len);
		}

		static int process_mdb(SCLPEvent event, MDBO mdbo)