Why does a thread not sleep ?

From: Jos Hulzink (josh@stack.nl)
Date: Thu Jan 16 2003 - 12:15:54 EST


In a driver, in the bottom half of an interrupt handler, I use
set_task_state (task, TASK_INTERRUPTIBLE) to make a task sleeping.
Sometimes (about 50 % of the cases), the task wakes up immediately again,
even though no signals are sent to the task. I tried TASK_UNINTERRUPTIBLE
and TASK_STOPPED too, but the same thing happens.

Can it be the task state is returned to TASK_RUNNING again in some
situations by other code ? Should I use locking, even on uniprocessor
systems ? Can a modification of the task state get lost in some situations
? I know about SMP related issues, but this doesn't even work on UP

In other words: I don't get it. Help would be appreciated.


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