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p_mutex_*: Implement init/lock/unlock/etc: #162

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p_mutex_*: Implement init/lock/unlock/etc: #162

wants to merge 2 commits into from

Commits on Jun 23, 2015

  1. p_mutex_*: Implement init/lock/unlock/etc: 

    Implement the p_mutex functions.

p_mutex_t is a uint32_t* -- We waste 23 bytes on it, but it's a
nice round size.

This follows in the form that pthreads uses. Each of these functions
does a quick NULL check to be sure things aren't bad (except for
p_mutex_create, which checks that we're not trying to initialize an
empty p_mutex_t)

Signed-off-by: Morgan Gangwere <[email protected]>
    @indrora
    indrora committed Jun 23, 2015
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  2. p_mutex_lock / p_mutex_trylock: race proofing. 

    Change up locking logic such that race conditions are
less of a problem.

in p_mutex_lock: spin until a lock is gotten *and* it
equals 1 with two nested loops and atomic operations only.

in p_mutex_trylock: fail early, but an atomic branch will
cause a small check to see if a race happened *and* the thread
asking for the mutex actually got the lock. No loops, only
returns.

Signed-off-by: Morgan Gangwere <[email protected]>
    @indrora
    indrora committed Jun 23, 2015
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