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Commit 883a3acf authored by Tony Luck's avatar Tony Luck
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[IA64] Re-implement spinaphores using ticket lock concepts 



Bound the wait time for the ptcg_sem by using similar idea to the
ticket spin locks.  In this case we have only one instance of a
spinaphore, so make it 8 bytes rather than try to squeeze it into
4-bytes to keep the code simpler (and shorter).

Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent 36a07902

arch/ia64/mm/tlb.c

+18 −6
Original line number Diff line number Diff line
@@ -100,24 +100,36 @@ wrap_mmu_context (struct mm_struct *mm) 
 * this primitive it can be moved up to a spinaphore.h header.

 */

struct spinaphore {

	atomic_t	cur;

	unsigned long	ticket;

	unsigned long	serve;

};



static inline void spinaphore_init(struct spinaphore *ss, int val)

{

	atomic_set(&ss->cur, val);

	ss->ticket = 0;

	ss->serve = val;

}



static inline void down_spin(struct spinaphore *ss)

{

	while (unlikely(!atomic_add_unless(&ss->cur, -1, 0)))

		while (atomic_read(&ss->cur) == 0)

	unsigned long t = ia64_fetchadd(1, &ss->ticket, acq), serve;



	if (time_before(t, ss->serve))

		return;



	ia64_invala();



	for (;;) {

		asm volatile ("ld4.c.nc %0=[%1]" : "=r"(serve) : "r"(&ss->serve) : "memory");

		if (time_before(t, serve))

			return;

		cpu_relax();

	}

}



static inline void up_spin(struct spinaphore *ss)

{

	atomic_add(1, &ss->cur);

	ia64_fetchadd(1, &ss->serve, rel);

}



static struct spinaphore ptcg_sem;