[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] grant_table: convert grant table rwlock to percpu rwlock
On 18/11/15 11:41, Jan Beulich wrote: >>>> On 18.11.15 at 12:23, <malcolm.crossley@xxxxxxxxxx> wrote: >> On 18/11/15 10:54, Jan Beulich wrote: >>> That's not how I understood it, the rwlock isn't per-pCPU (at least not >>> in what this patch does - it remains a per-domain one). The per-pCPU >>> object is a pointer to an rwlock, which gets made point to whatever >>> domain's rwlock the pCPU wants to own. >> >> This description is correct but it's important to note that the rwlock >> is only used by the writers and could be effectively replaced with a >> spinlock. > > While such replacement may indeed be possible (whether desirable > is another question), I'm pretty sure I saw readers taking the read > lock on the slow path. > You are right, the core code currently relies upon rw locks. Conceptually it may not need to but that's a different question as you state. Sorry for that mistake. Maybe it would be clearer if we created a percpu_rwlock_t which is really a rwlock_t. This would prevent accidental usage of the underlying rwlock_t by new grant table code. Malcolm > Jan > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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