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Micro optimise _callout_stop_safe() by removing dead code.

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The CS_DRAIN flag cannot be set at the same time like the async-drain function
pointer is set. These are orthogonal features. Assert this at the beginning
of the function.

Before:
        if (flags & CS_DRAIN) {
                /* FALLTHROUGH */
        } else if (xxx) {
                return yyy;
        }
        if (drain) {
                zzz = drain;
        }
After:
        if (flags & CS_DRAIN) {
                /* FALLTHROUGH */
        } else if (xxx) {
                return yyy;
        } else {
                if (drain) {
                        zzz = drain;
                }
        }

Reviewed by:	markj@
Tested by:	callout_test
Differential Revision:	https://reviews.freebsd.org/D26285
MFC after:	1 week
Sponsored by:	Mellanox Technologies // NVIDIA Networking
This commit is contained in:
Hans Petter Selasky 2020-09-02 09:44:00 +00:00
parent 72d849c761
commit 0d0053d7ed
1 changed files with 9 additions and 5 deletions
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14
sys/kern/kern_timeout.c
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@ -1075,6 +1075,9 @@ _callout_stop_safe(struct callout *c, int flags, callout_func_t *drain)
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
"calling %s", __func__);
KASSERT((flags & CS_DRAIN) == 0 || drain == NULL,
("Cannot set drain callback and CS_DRAIN flag at the same time"));
/*
* Some old subsystems don't hold Giant while running a callout_stop(),
* so just discard this check for the moment.
@ -1270,11 +1273,12 @@ again:
}
CC_UNLOCK(cc);
return ((flags & CS_EXECUTING) != 0);
}
CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
c, c->c_func, c->c_arg);
if (drain) {
cc_exec_drain(cc, direct) = drain;
} else {
CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
c, c->c_func, c->c_arg);
if (drain) {
cc_exec_drain(cc, direct) = drain;
}
}
KASSERT(!sq_locked, ("sleepqueue chain still locked"));
cancelled = ((flags & CS_EXECUTING) != 0);