Why page fault handler behaved this way? Please help!
Dear all, I am a kernel newbie who want's to learn more about memory management. Recently I'm doing some experiment on page fault handler. There happened something that I couldn't understand. From reading the book Understanding the Linux Kernel, I know that the kernel loads a page as late as possible. It's only happened when the program has to reference (read, write, or execute) a page yet the page is not in memory. However, when I traced all page faults in my test program, I found something strange. My test program is large enough, but there are only two page faults triggered in the code segment of the program, while most of the faults are not in code segment. At first I thought that perhaps the page is not the normal 4K page. Thus I turned off the PAE support in the config file. But the log remains unchanged. So why are there only 2 page faults in code segment? It shouldn't be like this in my opinion. Please help me. The attachment is my kernel log. Limited by the mail size, I couldn't upload my program, but I believe that the log is clear enough. Thank you very much. Best regards kernel_log Description: Binary data ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Query on the ci_udc driver for USB client implementation
Hello, I am currently implementing USB Host and client support for Freescale Vybrid platform in u-boot. I managed to get the host implementation working. For the host side, usb start calls usb_init(), which in turns call, usb_lowlevel_init(), from there into the ehic_hcd_init() of my implementation. So, setting up the necessary clocks and plls for USB in my implementation and then setting up the usb_ehci, ehci_hccr and echi_hcor structures was all. The flow and setup required i was able to trace. The USB client part is not clear to me. I was thinking i can use the ci_udc driver somehow to implement the client part. How can i use the ci_udc driver to implement client functionality?. From what i could see, the usb_gadget_driver_register() is suppose to be the first call. But, i couldn't trace from where this gets called or the flow and setup is suppose to be. OR Is a separate client driver required and nothing generic can be used akin to how it could be done for host? Sorry if i am asking this question in the wrong place. I couldn't find anyone in the u-boot IRC channel nor find something similar to the kernel-newbies mailing list. Hope i am asking the right questions. Sorry if this mail ends up two times in this list, i mistakenly tried sending it from the mail ID not registered with this mailing list. Thanks Regards, Sanchayan Maity. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
How can I wake up one process from the wait queue?
Hi, everyoneI am implementing a simple driver to experiment with wait queue.Two
or more read processes block until a write process changes a flag and call
wake_up_interruptible().I expect that a write process will only wake up one
read process.However, once a write process calls wake_up_interruptible() , all
the read processes are awaken. How can I wake up one process from the wait
queue? Here is the snippet of the simple dirver(just for experimenting, kernel
2.6.18):
static ssize_t rlwait_read(struct file *filp, char __user *userp, size_t size,
loff_t *off){struct rlwait_t *rock = (struct rlwait_t *)filp-private_data;
DECLARE_WAITQUEUE(wait, current);add_wait_queue(rock-r_wait_head,
wait);while (rock-r_flag == 0) {
set_current_state(TASK_INTERRUPTIBLE);schedule();}
remove_wait_queue(rock-r_wait_head, wait);
set_current_state(TASK_RUNNING);return 0;}
static ssize_t rlwait_write(struct file *filp, const char __user *userp, size_t
size, loff_t *off){struct rlwait_t *rock = (struct rlwait_t
*)filp-private_data;rock-r_flag = 1;
wake_up_interruptible(rock-r_wait_head);return size; }
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Re: How can I wake up one process from the wait queue?
Hi
You got to use exclusive wait queues here. Needs a bit more lines but
you can specify exactly how many tasks you want woken up.
You should be able to look it up easily on how to use it.
On Thu, Oct 30, 2014 at 2:02 PM, Rock Lee rocklee_...@sina.com wrote:
Hi, everyone
I am implementing a simple driver to experiment with wait queue.Two or more
read processes block until a write process changes a flag and call
wake_up_interruptible().I expect that a write process will only wake up one
read process.However, once a write process calls wake_up_interruptible() ,
all the read processes are awaken. How can I wake up one process from the
wait queue? Here is the snippet of the simple dirver(just for experimenting,
kernel 2.6.18):
static ssize_t rlwait_read(struct file *filp, char __user *userp, size_t
size, loff_t *off)
{
struct rlwait_t *rock = (struct rlwait_t *)filp-private_data;
DECLARE_WAITQUEUE(wait, current);
add_wait_queue(rock-r_wait_head, wait);
while (rock-r_flag == 0) {
set_current_state(TASK_INTERRUPTIBLE);
schedule();
}
remove_wait_queue(rock-r_wait_head, wait);
set_current_state(TASK_RUNNING);
return 0;
}
static ssize_t rlwait_write(struct file *filp, const char __user *userp,
size_t size, loff_t *off)
{
struct rlwait_t *rock = (struct rlwait_t *)filp-private_data;
rock-r_flag = 1;
wake_up_interruptible(rock-r_wait_head);
return size;
}
Thans in advice.
___
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---P.K.S
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Re: How can I wake up one process from the wait queue?
On Thursday 30 October 2014 02:02 PM, Rock Lee wrote: Hi, everyone I am implementing a simple driver to experiment with wait queue.Two or more read processes block until a write process changes a flag and call wake_up_interruptible().I expect that a write process will only wake up one read process.However, once a write process calls wake_up_interruptible() , all the read processes are awaken. How can I wake up one process from the wait queue? You can use exclusive wait queues, which wakes up only one process from the queue. Although the general idea that is followed is: all the process are woken up once the resource is made available. And then the access to that resource is guarded by a lock, which in turn allows only one process to access the resource. Rest of the processes are pushed backed to sleep(or busy wait). --- [ C-DAC is on facebook. Kindly follow us on the following url: https://www.facebook.com/CDACINDIA ] This e-mail is for the sole use of the intended recipient(s) and may contain confidential and privileged information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies and the original message. Any unauthorized review, use, disclosure, dissemination, forwarding, printing or copying of this email is strictly prohibited and appropriate legal action will be taken. --- --- [ C-DAC is on Social-Media too. Kindly follow us at: Facebook: https://www.facebook.com/CDACINDIA Twitter: @cdacindia ] This e-mail is for the sole use of the intended recipient(s) and may contain confidential and privileged information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies and the original message. Any unauthorized review, use, disclosure, dissemination, forwarding, printing or copying of this email is strictly prohibited and appropriate legal action will be taken. --- ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: [PATCH] staging: rtl8723au: Fix brace coding style issues reported by checkpatch
I am trying to improve my rep first through. Cheers Nick On 14-10-30 12:21 AM, Sudip Mukherjee wrote: On Thu, Oct 30, 2014 at 5:34 AM, nick xerofo...@gmail.com wrote: I don't mind waiting. I am just honestly trying to improve my rep here and actually(hopefully) get a job doing this full time. great , even if i want to get into a job where i can do this full time , and hopefully everyone here does, I dont want to discourage you , but considering your reputation (all over the world - maybe even outside this world) , that might be difficult. Cheers Nick On 14-10-29 04:45 AM, Scott Lovenberg wrote: On Wed, Oct 29, 2014 at 1:48 AM, Sudip Mukherjee sudipm.mukher...@gmail.com wrote: On Wed, Oct 29, 2014 at 11:38 AM, Scott Lovenberg scott.lovenb...@gmail.com wrote: On Wed, Oct 29, 2014 at 12:05 AM, Sudip Mukherjee sudipm.mukher...@gmail.com wrote: On Wed, Oct 29, 2014 at 7:31 AM, nick xerofo...@gmail.com wrote: Greg, That's fine, I was wondering how long Greg KH takes to get around to picking this up as he is very busy with other kernel work. it might take a long long time. i think he is very busy now. I have not seen his replies to patches in the kernel list for atleast last 3 weeks. [snip] ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies Nah. Greg KH is a robot. I'm firmly convinced that man doesn't sleep. If I didn't know better, I'd think he's a Cylon. well said. On a serious note; realistically, a two week window isn't unheard of for getting your patches to mainline. So long as you're not trying to mine is three weeks going on now. somehow i have managed to send my patches just at the beginning of the merge window. :( yesterday i saw Greg K-H releasing the stable patches , so i guess now he will be seeing the pending staging patches. It also depends on how many hops you are to the maintainer and how heavy their workload is. Sometimes you can directly submit to them, other times your patches will be passed through three trees before they see mainline. It all depends on what you're working on and who's in your circle. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
回复：Re: How can I wake up one process from the wait queue?
Hi, Raghavendra, pranjas: Thanks for your reply, add_wait_queue_exclusive() is perfect. - 原始邮件 - 发件人：Raghavendra ar...@cdac.in 收件人：kernelnewbies@kernelnewbies.org 主题：Re: How can I wake up one process from the wait queue? 日期：2014年10月30日 16点52分 On Thursday 30 October 2014 02:02 PM, Rock Lee wrote: Hi, everyone I am implementing a simple driver to experiment with wait queue.Two or more read processes block until a write process changes a flag and call wake_up_interruptible().I expect that a write process will only wake up one read process.However, once a write process calls wake_up_interruptible() , all the read processes are awaken. How can I wake up one process from the wait queue? You can use exclusive wait queues, which wakes up only one process from the queue. Although the general idea that is followed is: all the process are woken up once the resource is made available. And then the access to that resource is guarded by a lock, which in turn allows only one process to access the resource. Rest of the processes are pushed backed to sleep(or busy wait). --- ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
sched_clock generic for all architectures
Hi Gerg, I want know why this two commit id is not backported v3.10 1 . sched_clock: Make ARM's sched_clock generic for all architectures 2 . arch_timer: Move to generic sched_clock framework where as the 1 commit is already backported v3.11 I back ported these two commit id 3.10 arm cortex-a9 boot's fine, Is there any issue with this commit's if it is backported to v3.10. Regards, ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
