11-12-2007
To Porter:
I just realized that I also have to lock the file while reading as well to prevent write while reading...Thanks
To Smiling Dragon:
Thanks a lot for the pointer...I tried the sample program and thats exactly what I was looking for
Btw, where is the information that the file is locked stored ? How does another process (still using flock) know that a file is locked and has to sleep till unlocked ?
Thanks in advance.
J.
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LEARN ABOUT CENTOS
wait_event_interruptible_exclusive_locked_irq
WAIT_EVENT_INTERRUPT(9) Driver Basics WAIT_EVENT_INTERRUPT(9)
NAME
wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
SYNOPSIS
wait_event_interruptible_exclusive_locked_irq(wq, condition);
ARGUMENTS
wq
the waitqueue to wait on
condition
a C expression for the event to wait for
DESCRIPTION
The process is put to sleep (TASK_INTERRUPTIBLE) until the condition evaluates to true or a signal is received. The condition is checked
each time the waitqueue wq is woken up.
It must be called with wq.lock being held. This spinlock is unlocked while sleeping but condition testing is done while lock is held and
when this macro exits the lock is held.
The lock is locked/unlocked using spin_lock_irq/spin_unlock_irq functions which must match the way they are locked/unlocked outside of this
macro.
The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag set thus when other process waits process on the list if this process
is awaken further processes are not considered.
wake_up_locked has to be called after changing any variable that could change the result of the wait condition.
The function will return -ERESTARTSYS if it was interrupted by a signal and 0 if condition evaluated to true.
COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 WAIT_EVENT_INTERRUPT(9)