Commit f704f56a authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds

[PATCH] enable PREEMPT_BKL on !PREEMPT+SMP too

The only sane way to clean up the current 3 lock_kernel() variants seems to
be to remove the spinlock-based BKL implementations altogether, and to keep
the semaphore-based one only.  If we dont want to do that for whatever
reason then i'm afraid we have to live with the current complexity.  (but
i'm open for other cleanup suggestions as well.)

To explore this possibility we'll (at a minimum) have to know whether the
semaphore-based BKL works fine on plain SMP too.  The patch below enables
this.

The patch may make sense in isolation as well, as it might bring
performance benefits: code that would formerly spin on the BKL spinlock
will now schedule away and give up the CPU.  It might introduce performance
regressions as well, if any performance-critical code uses the BKL heavily
and gets overscheduled due to the semaphore.  I very much hope there is no
such performance-critical codepath left though.
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent cc19ca86
...@@ -13,7 +13,7 @@ config PREEMPT ...@@ -13,7 +13,7 @@ config PREEMPT
config PREEMPT_BKL config PREEMPT_BKL
bool "Preempt The Big Kernel Lock" bool "Preempt The Big Kernel Lock"
depends on PREEMPT depends on SMP || PREEMPT
default y default y
help help
This option reduces the latency of the kernel by making the This option reduces the latency of the kernel by making the
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment