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When a process calls wait_event_interruptible the process goes to sleep(assuming the condition is satisfied and there are no pending signals) the scheduler removes the process from the run queue to the wait queue.
When there is wake_up call how exactly and who removes the process from wait queue and keeps it in the run queue?
Thaks
The “wake_up call” is a system call done by another thread/process/task (some kernels put state on thread rather than process) with the thread/process/task to wake up in parameter. Because the system call is an interrupt (
int $0x80on Linux, until it was recently replaced bysysenterwhich is basically the same), thus entering the kernel, the scheduler will be called and the requested thred/process/task will be poped out the blocked queue and pushed into the ready queue. If this thread/process/task has the highest priority, it will eventually run when returning from the interrupt, therefore going directly from the blocked state to the running state.