If the lock is not acquired and has to spin *and* the second attempt
to acquire the lock fails, the delay time is not masked by the ticket
range mask. If the ticket number wraps around to zero, the result is
that the lock sampling delay is essentially infinite (due to casting
-1 to an unsigned int).
The fix: Always mask the difference between my_ticket and the current
ticket value before calculating the delay.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Architectures other than mips and x86 are not using ticket spinlocks.
Therefore, the contention on the lock is meaningless, since there is
nobody known to be waiting on it (arguably /fairly/ unfair locks).
Dummy it out to return 0 on other architectures.
Signed-off-by: Kyle McMartin <kyle@redhat.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
