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authorJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>2009-10-20 10:28:21 +0400
committerJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>2009-11-03 22:05:51 +0300
commit7825cf10e31c64ece3cac66fb01a742f1094da51 (patch)
tree45de3111641487d1deb18cfb86200113e2427b0b
parent973df35ed9ff7806403e793a2ad7e9bd4c2fd2a9 (diff)
downloadlinux-7825cf10e31c64ece3cac66fb01a742f1094da51.tar.xz
xen/hvc: make sure console output is always emitted, with explicit polling
We never want to rely on the hvc workqueue to emit output, because the most interesting output is when the kernel is broken. This will improve oops/crash/console message for better debugging. Instead, we force-poll until all output is emitted. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Stable Kernel <stable@kernel.org>
-rw-r--r--drivers/char/hvc_xen.c25
1 files changed, 24 insertions, 1 deletions
diff --git a/drivers/char/hvc_xen.c b/drivers/char/hvc_xen.c
index eba999f8598d..a6ee32b599a8 100644
--- a/drivers/char/hvc_xen.c
+++ b/drivers/char/hvc_xen.c
@@ -55,7 +55,7 @@ static inline void notify_daemon(void)
notify_remote_via_evtchn(xen_start_info->console.domU.evtchn);
}
-static int write_console(uint32_t vtermno, const char *data, int len)
+static int __write_console(const char *data, int len)
{
struct xencons_interface *intf = xencons_interface();
XENCONS_RING_IDX cons, prod;
@@ -76,6 +76,29 @@ static int write_console(uint32_t vtermno, const char *data, int len)
return sent;
}
+static int write_console(uint32_t vtermno, const char *data, int len)
+{
+ int ret = len;
+
+ /*
+ * Make sure the whole buffer is emitted, polling if
+ * necessary. We don't ever want to rely on the hvc daemon
+ * because the most interesting console output is when the
+ * kernel is crippled.
+ */
+ while (len) {
+ int sent = __write_console(data, len);
+
+ data += sent;
+ len -= sent;
+
+ if (unlikely(len))
+ HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
+ }
+
+ return ret;
+}
+
static int read_console(uint32_t vtermno, char *buf, int len)
{
struct xencons_interface *intf = xencons_interface();