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genirq: Clarify logic calculating bogus irqreturn_t values 

Although irqreturn_t is an enum, we treat it (and its enumeration
constants) as a bitmask.

However, bad_action_ret() uses a less-than operator to determine whether
an irqreturn_t falls within allowable bit values, which means we need to
know the signededness of an enum type to read the logic, which is
implementation-dependent.

This change explicitly uses an unsigned type for the comparison. We do
this instead of changing to a bitwise test, as the latter compiles to
increased instructions in this hot path.

It looks like we get the correct behaviour currently (bad_action_ret(-1)
returns 1), so this is purely a readability fix.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Link: http://lkml.kernel.org/r/1487219049-4061-1-git-send-email-jk@ozlabs.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Jeremy Kerr 2017-02-16 12:24:09 +08:00 committed by Thomas Gleixner
parent 2f44e29cef
commit 5d4bac9a5f
1 changed files with 3 additions and 1 deletions
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4
kernel/irq/spurious.c
View File

@ -175,7 +175,9 @@ static void poll_spurious_irqs(unsigned long dummy)
static inline int bad_action_ret(irqreturn_t action_ret)
{
if (likely(action_ret <= (IRQ_HANDLED | IRQ_WAKE_THREAD)))
unsigned int r = action_ret;
if (likely(r <= (IRQ_HANDLED | IRQ_WAKE_THREAD)))
return 0;
return 1;
}