hi all, i've heard that the linux kernel is preemptive from 2.5 onwards.... so can an ISR be preempted by the kernel. as i understand an ISR doest not have a process context, so then what can preempt it????
thanx
- /dev/mandeep
-----Original Message----- From: kernelnewbies-bounce@nl.linux.org [mailto:kernelnewbies-bounce@nl.linux.org]On Behalf Of Tyler Sent: Friday, June 04, 2004 1:35 PM To: kernelnewbies@nl.linux.org Subject: Re: sharing data
1. I share a data between a kernel thread and an ISR. ( this is a uniprocessor system). In kernel thread I do spin_lock_irqsave
and then unlocking. Where as accessing the data from the ISR I do not use any spin lock coz I know when the ISR is running the kernel thread does not get a chance to run. Am I right ???
It is only true if you are not in a SMP environment (and think of those who have multiprocessors) and also if you are not in a preemptive envirnoment (Linux kernel is preemptive since 2.5). So you should protect your data in the ISR too.
2. I want to implement a message quque send and recv routine between two kernel threads. ( here I can not use the standard message quques)
What I do is in recv call I check if there is any message in the queue. If no then I sleep on a wait queue.
While sending a message I always add the message to the queue and and use wake up call on wait queue.
Is my implementation leak proff?..or there are some flaws???
Yes it looks good :)
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-- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
