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    SubjectRe: deadlock avoidance?
    On Wed, Dec 08, 1999, Davide Libenzi <dlibenzi@maticad.it> wrote:
    > Wednesday, December 08, 1999 1:53 AM
    > Johannes Erdfelt <jerdfelt@sventech.com> wrote :
    > > > All pid and count modify fall inside 1) a nested lock ( ie. the task
    > > > already own the lock : ++lock->count )
    > > > 2) a lock acquired : lock->pid = getpid() and ++lock->count
    > >
    > > The setting is, but not all of the reading.
    >
    > There is not test & set operations other than spin_... in my code.
    > Look at it better and try to find a sequence of operations that stall it.
    >
    > struct s_nested_lock {
    > spinlock_t lock;
    > short int pid;
    > short int count;
    > };
    >
    > #define nested_lock(lock, flags) \
    > if (lock->pid == getpid()) { \
    > ++lock->count; \
    > } else { \
    > spin_lock_irqsave(&lock->lock, flags); \
    > ++lock->count; \
    > lock->pid = getpid(); \
    > }
    >
    > #define nested_unlock(lock, flags) \
    > if (--lock->count == 0) { \
    > lock->pid = 0; \
    > spin_unlock_irqrestore(&lock->lock, flags); \
    > }

    Hate to bother you again, but I'm running into some issues.

    getpid() is no longer implemented in 2.3 and using current->pid
    sometimes results in 0 which is causing the logic to fail (since we set
    the pid to 0 if the lock is not acquired)

    Is there anyway to get a unique pid like number under 2.3 kernels?

    JE


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