Messages in this thread Patch in this message | | | Subject | Re: [PATCH -v3] use per cpu data for single cpu ipi calls | From | Peter Zijlstra <> | Date | Fri, 30 Jan 2009 13:48:51 +0100 |
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On Fri, 2009-01-30 at 13:38 +0100, Jens Axboe wrote:
> > if (!wait) { > > + /* > > + * We are calling a function on a single CPU > > + * and we are not going to wait for it to finish. > > + * We first try to allocate the data, but if we > > + * fail, we fall back to use a per cpu data to pass > > + * the information to that CPU. Since all callers > > + * of this code will use the same data, we must > > + * synchronize the callers to prevent a new caller > > + * from corrupting the data before the callee > > + * can access it. > > + * > > + * The CSD_FLAG_LOCK is used to let us know when > > + * the IPI handler is done with the data. > > + * The first caller will set it, and the callee > > + * will clear it. The next caller must wait for > > + * it to clear before we set it again. This > > + * will make sure the callee is done with the > > + * data before a new caller will use it. > > + * We use spinlocks to manage the callers. > > + */ > > That last sentence appears stale now, since there's no locking involved > for the per-cpu csd.
Gah, I edited that, and generated the patch using
# git diff --stat -p 4f4b6c1a94a8735bbdc030a2911cf395495645b6.. kernel/smp.c | xclip
on Ingo's tip/master. However it seems such a diff does not include non-commited changes, even though a regular git diff does:
# git diff kernel/smp.c diff --git a/kernel/smp.c b/kernel/smp.c index 9eead6c..bbedbb7 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -251,7 +251,6 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info, * it to clear before we set it again. This * will make sure the callee is done with the * data before a new caller will use it. - * We use spinlocks to manage the callers. */ data = kmalloc(sizeof(*data), GFP_ATOMIC); if (data) What is the recommended way to do such a diff?
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