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qemu-char: Keep pty slave file descriptor open until the master is closed 

If a process opens the slave pts device, writes data to it, then
immediately closes it, the data doesn't reliably get delivered to the
emulated serial port. This seems to be because a read of the master
pty device returns EIO on Linux if no process has the pts device open,
even when data is waiting "in the pipe".

A fix seems to be for QEMU to keep the pts file descriptor open until
the pty is closed, as per the below patch.

Signed-off-by: Ashley Jonathan <jonathan.ashley@altran.com>
Message-Id: <AC19797808C8D548ABDE0CA4A97AA30A30DEB409@XMB-DCFR-37.europe.corp.altran.com>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2016-01-19 14:13:29 +01:00
parent 5b82b703b6
commit 34689e206a
1 changed files with 3 additions and 1 deletions
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4
qemu-char.c
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@ -1171,6 +1171,7 @@ typedef struct {
int connected;
guint timer_tag;
guint open_tag;
int slave_fd;
} PtyCharDriver;
static void pty_chr_update_read_handler_locked(CharDriverState *chr);
@ -1347,6 +1348,7 @@ static void pty_chr_close(struct CharDriverState *chr)
qemu_mutex_lock(&chr->chr_write_lock);
pty_chr_state(chr, 0);
close(s->slave_fd);
object_unref(OBJECT(s->ioc));
if (s->timer_tag) {
g_source_remove(s->timer_tag);
@ -1374,7 +1376,6 @@ static CharDriverState *qemu_chr_open_pty(const char *id,
return NULL;
}
close(slave_fd);
qemu_set_nonblock(master_fd);
chr = qemu_chr_alloc(common, errp);
@ -1399,6 +1400,7 @@ static CharDriverState *qemu_chr_open_pty(const char *id,
chr->explicit_be_open = true;
s->ioc = QIO_CHANNEL(qio_channel_file_new_fd(master_fd));
s->slave_fd = slave_fd;
s->timer_tag = 0;
return chr;