From: Daniel P. Berrange Date: Tue, 6 Sep 2016 13:56:03 +0000 (+0100) Subject: sclpconsolelm: remove bogus check for -EAGAIN X-Git-Tag: qemu-xen-4.9.0-rc1~200^2~20 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=7983e829336f68b6df6952dd4b03493b1486fcf5;p=qemu-xen.git 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 Signed-off-by: Daniel P. Berrange Message-Id: <1473170165-540-3-git-send-email-berrange@redhat.com> Signed-off-by: Paolo Bonzini --- diff --git a/hw/char/sclpconsole-lm.c b/hw/char/sclpconsole-lm.c index a22ad8d016..dbe753147b 100644 --- a/hw/char/sclpconsole-lm.c +++ b/hw/char/sclpconsole-lm.c @@ -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)