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Re: timer irqs when no preemption

2007/2/2, Bahadir Balban <bahadir.balban@xxxxxxxxx>:
Hi,

When preemption is disabled, what happens if a timer interrupt occurs
when a process is in a system call? I would guess the handler would
update process times, and if a schedule is pending, it occurs as soon
as the process returns from the system call. Is that correct?


Yes, I think so. In this case, the timer interrupt causes the thread
flag TIF_NEED_RESCHED being set, which in turn causes context switch
just before the system call returns.

Another question - the irqs are disabled at times (like when a
spinlock is held). Does this cause any lost timer ticks?


I guess so.

Thanks,
Bahadir

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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/