Re: [PATCH 8/8] membarrier: Rewrite sync_core_before_usermode() and improve documentation

On Wed, Jun 16, 2021, at 11:52 AM, Andy Lutomirski wrote:

On 6/15/21 9:45 PM, Nicholas Piggin wrote:

quoted

Excerpts from Andy Lutomirski's message of June 16, 2021 1:21 pm:

quoted

The old sync_core_before_usermode() comments suggested that a non-icache-syncing
return-to-usermode instruction is x86-specific and that all other
architectures automatically notice cross-modified code on return to
userspace.

quoted

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+/*
+ * XXX: can a powerpc person put an appropriate comment here?
+ */
+static inline void membarrier_sync_core_before_usermode(void)
+{
+}
+
+#endif /* _ASM_POWERPC_SYNC_CORE_H */

powerpc's can just go in asm/membarrier.h

$ ls arch/powerpc/include/asm/membarrier.h
ls: cannot access 'arch/powerpc/include/asm/membarrier.h': No such file
or directory

Which is because I deleted it.  Duh.  I'll clean this up.

quoted

/*
 * The RFI family of instructions are context synchronising, and
 * that is how we return to userspace, so nothing is required here.
 */

Thanks!