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| author | attilio <attilio@FreeBSD.org> | 2012-12-09 04:54:22 +0000 |
|---|---|---|
| committer | attilio <attilio@FreeBSD.org> | 2012-12-09 04:54:22 +0000 |
| commit | 230b7eda6f0ca8c9257eb05130deb2b22efcc622 (patch) | |
| tree | 3cb84ac1cacb4ad4963cf0e7cdbdf19c56c486fb | |
| parent | 2961cca7115ab05fda3222d813523d134ac42adc (diff) | |
| download | FreeBSD-src-230b7eda6f0ca8c9257eb05130deb2b22efcc622.zip FreeBSD-src-230b7eda6f0ca8c9257eb05130deb2b22efcc622.tar.gz | |
Add a comment on why inlining critical_enter() may not be a good idea
for the general case.
Reviewed by: bde
MFC after: 1 week
| -rw-r--r-- | sys/kern/kern_switch.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/sys/kern/kern_switch.c b/sys/kern/kern_switch.c index 885dc22..d0009b1 100644 --- a/sys/kern/kern_switch.c +++ b/sys/kern/kern_switch.c @@ -176,6 +176,12 @@ retry: /* * Kernel thread preemption implementation. Critical sections mark * regions of code in which preemptions are not allowed. + * + * It might seem a good idea to inline critical_enter() but, in order + * to prevent instructions reordering by the compiler, a __compiler_membar() + * would have to be used here (the same as sched_pin()). The performance + * penalty imposed by the membar could, then, produce slower code than + * the function call itself, for most cases. */ void critical_enter(void) |
