Hi on wed 7th sep Christopher Harvey wrote
It means that it can't be swapped to your swap partition, even if you're not using it.
this thing I understood it pretty well but what about the line "Therefore, every byte of memory you consume is one less byte of available physical memory".What is the meaning of this line and why it is so. On Tue, Sep 6, 2011 at 9:30 PM, <kernelnewbies-request@kernelnewbies.org>wrote:
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Today's Topics:
1. Re: Re: Regarding threaded irq and normal irq (anish singh) 2. CRC calculation in Module.symvers (Shakthi Kannan) 3. Re: Finding physical and logical core number in a kernel module ? (Alexandre Courbot) 4. How to identify Connected USB Storage device (Harddisk, flash Memory or SSD) (mani) 5. Paging of Kernel Memory (Vijay Chauhan) 6. Re: Paging of Kernel Memory (Christopher Harvey)
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Message: 1 Date: Tue, 6 Sep 2011 13:57:22 +0530 From: anish singh <anish198519851985@gmail.com> Subject: Re: Re: Regarding threaded irq and normal irq To: Mulyadi Santosa <mulyadi.santosa@gmail.com> Cc: Greg KH <greg@kroah.com>, tglx@linutronix.de, sandeep kumar <coolsandyforyou@gmail.com>, kernelnewbies@kernelnewbies.org Message-ID: <CAK7N6voUN+b8nj=nQNoU1wGVr=b9jCm+0Q43eHg7bPLcgB4Nzw@mail.gmail.com
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On Tue, Sep 6, 2011 at 10:59 AM, anish singh <anish198519851985@gmail.com> wrote:
On Tue, Sep 6, 2011 at 10:51 AM, Mulyadi Santosa <mulyadi.santosa@gmail.com> wrote:
Hi :)
On 06/09/2011, sandeep kumar <coolsandyforyou@gmail.com> wrote:
Hmm..But when i tried to take a mutex lock in threaded_irq, it is throwing a warning message "BUG: sleeping function called from invalid context"... So i was wondering which way it is..
Please don't top post :)
Anyway, regarding that "BUG:" message, could it be that mutex function mistakenly assume it's called inside top half, thus bails out since How can mutex assume? IMHO the message would have printed because sleeping would be forbidden there but again AFAIK in the threaded handler we can do I2C transactions which can sleep.So kind of paradox there.
something like using in_irq() inside the threaded irq handler? I think after going thorough the code of mutex_lock we can find out the reason why it is printing the warning eventhough we are calling it in a threaded handler i.e. kernel thread.
From the code: 126 /** 127 * might_sleep - annotation for functions that can sleep 128 * 129 * this macro will print a stack trace if it is executed in an atomic 130 * context (spinlock, irq-handler, ...).
129 line no is important. This might_sleep is called by mutex_lock function and in the defintion of __might_sleep i found below code.I think this below if condition is false because irqs_disabled is true.This causes the warning.
if ((preempt_count_equals(preempt_offset) && !irqs_disabled()) || system_state != SYSTEM_RUNNING || oops_in_progress) return;
Hope i am right?
ps:I have seen the code where sandeep is doing the taking the mutex lock. He is taking mutex lock at the beginging of the handler and releasing at the end.
sleeping is forbidden there? which mutex function do you use? (sorry I don't follow every locking functions exist now)
-- regards,
Mulyadi Santosa Freelance Linux trainer and consultant
blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com
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Message: 2 Date: Tue, 6 Sep 2011 12:41:24 +0530 From: Shakthi Kannan <shakthimaan@gmail.com> Subject: CRC calculation in Module.symvers To: kernelnewbies@kernelnewbies.org Message-ID: <CABG-yt2W02ToqJJ=-n773Lg-JCRnDYc7qzA0HsCw+morgnSx8Q@mail.gmail.com
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Greetings!
I would like to know as to:
1. How the CRC is computed for an exported symbol in the Linux kernel, and 2. Given a kernel .c file, how can I obtain the CRC checksums for a symbol.
For linux-3.0.2 (example), I compiled with CONFIG_MODVERSIONS=y, and running make built vmlinux, and generated the Module.symvers file. I believe genksyms is used to generate the CRC information.
I had referred the "Kernel Symbols and CONFIG_MODVERSIONS" documentation [1] written by Mark McLoughlin. I tried the following in the top-level kernel sources:
$ gcc -E -D__GENKSYMS__ -DCONFIG_MODVERSIONS -DEXPORT_SYMTAB crypto/api.c -I/tmp/linux-3.0.2/include -I/tmp/linux-3.0.2/arch/x86/include | ./scripts/genksyms/genksyms
and I get the following error output:
=== Output ===
/tmp/linux-3.0.2/include/linux/jiffies.h:43:42: error: division by zero in #if In file included from /tmp/linux-3.0.2/include/linux/tracepoint.h:19:0, from /tmp/linux-3.0.2/include/linux/module.h:18, from crypto/api.c:22: /tmp/linux-3.0.2/include/linux/rcupdate.h:160:2: error: #error "Unknown RCU implementation specified to kernel configuration" In file included from /tmp/linux-3.0.2/include/linux/module.h:21:0, from crypto/api.c:22: /tmp/linux-3.0.2/arch/x86/include/asm/module.h:59:2: error: #error unknown processor family
=== End ===
The documentation for genksyms is old, and now there is no -k option?
Appreciate any inputs in this regard,
Thanks!
SK
[1] Kernel Symbols and CONFIG_MODVERSIONS. http://www.skynet.ie/~mark/pub/symbols.txt
-- Shakthi Kannan http://www.shakthimaan.com
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Message: 3 Date: Tue, 6 Sep 2011 16:14:19 +0900 From: Alexandre Courbot <gnurou@gmail.com> Subject: Re: Finding physical and logical core number in a kernel module ? To: Vaibhav Jain <vjoss197@gmail.com> Cc: kernelnewbies@kernelnewbies.org Message-ID: <CAAVeFu+h9=-roQcJaoh_d4XNbm8BtqtbQRR7qrWgx0B-k27dHA@mail.gmail.com
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I agree that the kernel module is not restricted to any core but is it possible that whenever it is executed it gives the core number whichever is executing it ?
Have a look at the end of include/linux/smp.h: smp_processor_id() gives you the number of the current executing CPU. get_cpu() will do the same and will also disable preemption so that you will stay on that CPU until put_cpu() is called.
From user-space, you can use sched_getcpu() to obtain the same information.
Hope this helps, Alex.
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Message: 4 Date: Tue, 6 Sep 2011 16:02:33 +0530 From: mani <manishrma@gmail.com> Subject: How to identify Connected USB Storage device (Harddisk, flash Memory or SSD) To: kernelnewbies@kernelnewbies.org Message-ID: <CAB+TZU93_edNTfbNVKvQdgWiJxDTNHWWunNT6VNbHP+=RTixfw@mail.gmail.com
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Hi all,
Is there any way to find out the type of the connected USB disk (Hard disk/SDD)?
AFAIK there is a significant performance difference in Harddisk/SDD devices.
Previously i though that the rotational flag in the sysfs will distinguish them but it is same for both the types
#cat /sys/block/sda/queue/rotational 1 for both flash & HDD
Is there any way to distinguish the USB Harddisk or SDD drives ?
Thanks & Regards, Manish