On 2016-08-25 6:30 PM, Jianxun Zhang wrote:
We try to make this change a generic extension, but it is
actually for a corner case. When a VM (qemu) gets a very limited
cpu bandwidth from host, which could be under a heavy load, the
existing 5000 ms timeout could occur and trigger error messages
in the task function's callers.
This change adds a new timeout parameter so that we can tweak
the value as a workaround or for troubleshooting purposes. In
the infinite wait case, A warning message is printed at 5000ms
interval.
In real world, the current 5 sec is generous enough for a video
request in my opinion, so this change could not be very useful.
This looks fine to me.
I'm putting the finishing touches on the 4.8 kernel, and will merge
this shortly.
Bruce
Upstream Status: Inappropriate
Signed-off-by: Jianxun Zhang <jianxun.zh...@linux.intel.com>
---
Amend Upstream Status: Unnecessary->Inappropriate in commit message per
Saul's suggestion.
drivers/video/fbdev/uvesafb.c | 28 ++++++++++++++++++++++------
include/video/uvesafb.h | 4 +++-
2 files changed, 25 insertions(+), 7 deletions(-)
diff --git a/drivers/video/fbdev/uvesafb.c b/drivers/video/fbdev/uvesafb.c
index 13bbb61..bd26813 100644
--- a/drivers/video/fbdev/uvesafb.c
+++ b/drivers/video/fbdev/uvesafb.c
@@ -40,6 +40,7 @@ static struct fb_fix_screeninfo uvesafb_fix = {
.visual = FB_VISUAL_TRUECOLOR,
};
+static int task_timeout = UVESAFB_TIMEOUT; /* timeout [ms] of task execution */
static int mtrr = 3; /* enable mtrr by default */
static bool blank = 1; /* enable blanking by default */
static int ypan = 1; /* 0: scroll, 1: ypan, 2: ywrap */
@@ -143,7 +144,9 @@ static int uvesafb_exec(struct uvesafb_ktask *task)
struct cn_msg *m;
int err;
int len = sizeof(task->t) + task->t.buf_len;
-
+ int forever_wait = task_timeout < 0 ? 1 : 0;
+ /* For infinite wait case, set interval to the legacy 5000 ms */
+ int timeout = forever_wait ? 5000 : task_timeout;
/*
* Check whether the message isn't longer than the maximum
* allowed by connector.
@@ -212,11 +215,19 @@ static int uvesafb_exec(struct uvesafb_ktask *task)
err = 0;
if (!err && !(task->t.flags & TF_EXIT)) {
- err = !wait_for_completion_timeout(task->done,
- msecs_to_jiffies(UVESAFB_TIMEOUT));
- if (err)
- printk_ratelimited(KERN_ERR "uvesafb: %u ms task timeout
error\n",
- UVESAFB_TIMEOUT);
+ do {
+ err = !wait_for_completion_timeout(task->done,
+ msecs_to_jiffies(timeout));
+ if (err)
+ printk_ratelimited(
+ KERN_WARNING
+ "uvesafb: %u ms task
timeout%s\n",
+ timeout,
+ forever_wait ?
+ ", infinitely waiting." : ".");
+ else
+ break;
+ } while (forever_wait);
}
mutex_lock(&uvfb_lock);
@@ -1840,6 +1851,8 @@ static int uvesafb_setup(char *options)
while ((this_opt = strsep(&options, ",")) != NULL) {
if (!*this_opt) continue;
+ if (!strncmp(this_opt, "task_timeout", 12))
+ task_timeout = simple_strtol(this_opt+12, NULL, 0);
if (!strcmp(this_opt, "redraw"))
ypan = 0;
else if (!strcmp(this_opt, "ypan"))
@@ -1986,6 +1999,9 @@ static const struct kernel_param_ops param_ops_scroll = {
};
#define param_check_scroll(name, p) __param_check(name, p, void)
+module_param(task_timeout, int, 0400);
+MODULE_PARM_DESC(task_timeout,
+ "Timeout [ms] of a task's completion, or set to any negative value to
infinitely wait");
module_param_named(scroll, ypan, scroll, 0);
MODULE_PARM_DESC(scroll,
"Scrolling mode, set to 'redraw', 'ypan', or 'ywrap'");
diff --git a/include/video/uvesafb.h b/include/video/uvesafb.h
index 30f5362..bfd1982 100644
--- a/include/video/uvesafb.h
+++ b/include/video/uvesafb.h
@@ -88,7 +88,9 @@ struct vbe_mode_ib {
#define UVESAFB_DEFAULT_MODE "640x480-16"
-/* How long to wait for a reply from userspace [ms] */
+/* How long to wait for a reply from userspace [ms]
+ * This is the default value of module param task_timeout
+ */
#define UVESAFB_TIMEOUT 5000
/* Max number of concurrent tasks */
--
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