[PATCH for-4.9] tools/xenconsoled: Preserve errno while rotating logfile handles

* [PATCH for-4.9] tools/xenconsoled: Preserve errno while rotating logfile handles
@ 2017-05-16 13:57 Andrew Cooper
  2017-05-16 13:58 ` Ian Jackson
  0 siblings, 1 reply; 3+ messages in thread
From: Andrew Cooper @ 2017-05-16 13:57 UTC (permalink / raw)
  To: Xen-devel; +Cc: Andrew Cooper, Julien Grall, Ian Jackson, Wei Liu

The logic to optionally exit after a poll() error relies on errno, but
handle_log_reload() does not preserve it.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Julien Grall <julien.grall@arm.com>

For some reason which we haven't tracked down completely yet, an NTP time step
appears to reliably cause xenconsoled to exit, citing "Failure in poll
xs_handle: %d (%s)" with ENOENT.  The NTP time step almost certainly results
in log rotation, but I haven't identifed where the ENOENT came from.
---
 tools/console/daemon/io.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/console/daemon/io.c b/tools/console/daemon/io.c
index 7e6a886..7e474bb 100644
--- a/tools/console/daemon/io.c
+++ b/tools/console/daemon/io.c
@@ -1117,8 +1117,12 @@ void handle_io(void)
 		ret = poll(fds, nr_fds, next_timeout ? poll_timeout : -1);
 
 		if (log_reload) {
+			int saved_errno = errno;
+
 			handle_log_reload();
 			log_reload = 0;
+
+			errno = saved_errno;
 		}
 
 		/* Abort if poll failed, except for EINTR cases
-- 
2.1.4


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