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xen/hvc: make sure console output is always emitted, with explicit polling

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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>
This commit is contained in:
Jeremy Fitzhardinge 2009-10-20 15:28:21 +09:00
parent 973df35ed9
commit 7825cf10e3
1 changed files with 24 additions and 1 deletions
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25
drivers/char/hvc_xen.c
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@ -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();