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uvesafb: provide option to specify timeout for task completion

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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.

Upstream Status: Inappropriate

Signed-off-by: Jianxun Zhang <jianxun.zhang@linux.intel.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
This commit is contained in:
Jianxun Zhang 2016-08-25 15:30:55 -07:00 committed by Bruce Ashfield
parent a0ed481686
commit ece5aeead8
2 changed files with 25 additions and 7 deletions
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24
drivers/video/fbdev/uvesafb.c
View File

@ -44,6 +44,7 @@ static const 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 = true; /* enable blanking by default */
static int ypan = 1; /* 0: scroll, 1: ypan, 2: ywrap */
@ -147,7 +148,9 @@ 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.
@ -214,11 +217,19 @@ static int uvesafb_exec(struct uvesafb_ktask *task)
err = 0;
if (!err && !(task->t.flags & TF_EXIT)) {
do {
err = !wait_for_completion_timeout(task->done,
msecs_to_jiffies(UVESAFB_TIMEOUT));
msecs_to_jiffies(timeout));
if (err)
printk_ratelimited(KERN_ERR "uvesafb: %u ms task timeout error\n",
UVESAFB_TIMEOUT);
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);
@ -1823,6 +1834,8 @@ 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"))
@ -1966,6 +1979,9 @@ 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'");

4
include/video/uvesafb.h
View File

@ -89,7 +89,9 @@ 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 */