haraldwolff/qemu-patch-raspberry4
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sclpconsolelm: remove bogus check for -EAGAIN

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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>
This commit is contained in:
Daniel P. Berrange 2016-09-06 14:56:03 +01:00 committed by Paolo Bonzini
parent b72981b910
commit 7983e82933
1 changed files with 3 additions and 18 deletions
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21
hw/char/sclpconsole-lm.c
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@ -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)