Re: [PATCH] powerpc/tm: Clean up duplication of code

On Wed, 2016-05-11 at 17:44 +1000, Rashmica wrote:

On 11/05/16 15:03, Balbir Singh wrote:

quoted

On 11/05/16 14:55, Rashmica Gupta wrote:

quoted

The same logic for tm_abort appears twice, so pull it out into a
function.

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 7635b1c6b5da..1cef8f5aee9b 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c

@@ -1318,6 +1318,25 @@ out_exit:
  	local_irq_restore(flags);
  }
  
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+	/* Transactions are not aborted by tlbiel, only tlbie.

Can you fix up the comment formatting while you're there, should be:

/*
 * Transactions are not aborted by tlbiel, only tlbie.

quoted

quoted

+	 * Without, syncing a page back to a block device w/ PIO could pick up
+	 * transactional data (bad!) so we force an abort here.  Before the
+	 * sync the page will be made read-only, which will flush_hash_page.
+	 * BIG ISSUE here: if the kernel uses a page from userspace without
+	 * unmapping it first, it may see the speculated version.
+	 */
+static inline void abort_tm(int local)
+{
+	if (local && cpu_has_feature(CPU_FTR_TM) &&
+	    current->thread.regs &&
+	    MSR_TM_ACTIVE(current->thread.regs->msr)) {
+		tm_enable();
+		tm_abort(TM_CAUSE_TLBI);
+	}
+}

While your at this do

#else

static inline void abort_tm(int local)
{
}

If I'm doing that, wouldn't it make more sense to write:

+static inline void abort_tm(int local)

It needs a better name. Perhaps tlb_flush_abort_tm() ?

In this case it would make some sense.

But the goal is "no #ifdef's in C code", which that would violate.

And if you have two functions that need to be inside the #ifdef then the above
doesn't work anymore.

So the preferred style is:

  #ifdef CONFIG_FOO
  static void foo(int bar)
  {
  	...
  }
  #else /* !CONFIG_FOO */
  static inline foo(int bar) { }
  #endif


And when it expands you end up with:

  #ifdef CONFIG_FOO
  static void foo(int bar)
  {
  	...
  }

  static void foo_new(int bar)
  {
  	...
  }
  #else /* !CONFIG_FOO */
  static inline foo(int bar) { }
  static inline foo_new(int bar) { }
  #endif


cheers