On Mon, Oct 29, 2012 at 7:35 AM, Mathieu Desnoyers
[off-list ref] wrote:

* Sasha Levin (levinsasha928@gmail.com) wrote:

quoted

Switch tracepoints to use the new hashtable implementation. This reduces the amount of
generic unrelated code in the tracepoints.

Signed-off-by: Sasha Levin <redacted>
---
 kernel/tracepoint.c | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index d96ba22..854df92 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c

@@ -26,6 +26,7 @@
 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/static_key.h>
+#include <linux/hashtable.h>

 extern struct tracepoint * const __start___tracepoints_ptrs[];
 extern struct tracepoint * const __stop___tracepoints_ptrs[];

@@ -49,8 +50,7 @@ static LIST_HEAD(tracepoint_module_list);
  * Protected by tracepoints_mutex.
  */
 #define TRACEPOINT_HASH_BITS 6
-#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
-static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
+static DEFINE_HASHTABLE(tracepoint_table, TRACEPOINT_HASH_BITS);

[...]

quoted

@@ -722,6 +715,8 @@ struct notifier_block tracepoint_module_nb = {

 static int init_tracepoints(void)
 {
+     hash_init(tracepoint_table);
+
      return register_module_notifier(&tracepoint_module_nb);
 }
 __initcall(init_tracepoints);

So we have a hash table defined in .bss (therefore entirely initialized
to NULL), and you add a call to "hash_init", which iterates on the whole
array and initialize it to NULL (again) ?

This extra initialization is redundant. I think it should be removed
from here, and hashtable.h should document that hash_init() don't need
to be called on zeroed memory (which includes static/global variables,
kzalloc'd memory, etc).

This was discussed in the previous series, the conclusion was to call
hash_init() either way to keep the encapsulation and consistency.

It's cheap enough and happens only once, so why not?


Thanks,
Sasha

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