> On Sep 1, 2016, at 8:06 AM, Bruce Ashfield <bruce.ashfi...@windriver.com>
> wrote:
>
> I'm finally back to looking at this.
>
> One question. What kernel version is this for ? Them all (4.*) ?
More background information is in:
https://bugzilla.yoctoproject.org/show_bug.cgi?id=8245
I assume this change is for all kernel versions in linux-yocto. The
test was done with 4.4.15 kernel on qemu VM.
Sorry for V2 lost this piece in V1’s mail.
>
> Bruce
>
> On 2016-08-25 06:30 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.
>>
>> 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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