On Thu, 11 Aug 2005, Bodo Eggert wrote:
> Ukil a <[email protected]> wrote:
>
>> Now I had the doubt that if the the syscall
>> implementation is very large will the scheduling and
>> other interrupts be blocked for the whole time till
>> the process returns from the ISR (because in an ISR by
>> default the interrupts are disabled unless "sti" is
>> called explicitly)?
>
> According to my documentation it isn't. A software interrupt is a far call
> with an extra pushf, and a hardware interrupt is protected against recursion
> by the PIC, not by an interrupt flag.
> --
Every interrupt software, or hardware, results in the branched
procedure being executed with the interrupts OFF. That's why
one of the first instructions in the kernel entry for a syscall
is 'sti' to turn them back on. Look at entry.S, line 182. This
occurs any time a trap occurs as well (Page 26-168, i486
Programmer's reference manual). FYI, this is helpful when
designing/debugging complex interrupt-service routines since
you can execute the interrupt with a software 'INT' instruction
(with the correct offset from the IRQ you are using). The software
doesn't 'know' where the interrupt came from, HW or SW.
Cheers,
Dick Johnson
Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips).
Warning : 98.36% of all statistics are fiction.
.
I apologize for the following. I tried to kill it with the above dot :
****************************************************************
The information transmitted in this message is confidential and may be privileged. Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited. If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to [email protected] - and destroy all copies of this information, including any attachments, without reading or disclosing them.
Thank you.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
| |
 |