On 2020-11-24, HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx> wrote:
>> After looking more closely, I see that your patch is still using the
>> old state flags. With the current version, there is now a value-based
>> state field.
>
> Thank you for pointing it out! Could you submit a follow-up patch?
I have attached a follow-up patch. It is pretty much the exact same
patch as the one I sent for "crash".
John Ogness
>From 58396867cb3bfd1ca060cf5eb3a910d7f8c192c2 Mon Sep 17 00:00:00 2001
From: John Ogness <john.ogness@xxxxxxxxxxxxx>
Date: Wed, 25 Nov 2020 10:10:31 +0106
Subject: [PATCH] printk: use committed/finalized state values
The ringbuffer entries use 2 state values (committed and finalized)
rather than a single flag to represent being available for reading.
Copy the definitions and state lookup function directly from the
kernel source and use the new states.
Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx>
---
printk.c | 48 +++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 41 insertions(+), 7 deletions(-)
diff --git a/printk.c b/printk.c
index 8e00901..9cecbd1 100644
--- a/printk.c
+++ b/printk.c
@@ -1,12 +1,6 @@
#include "makedumpfile.h"
#include <ctype.h>
-#define DESC_SV_BITS (sizeof(unsigned long) * 8)
-#define DESC_COMMITTED_MASK (1UL << (DESC_SV_BITS - 1))
-#define DESC_REUSE_MASK (1UL << (DESC_SV_BITS - 2))
-#define DESC_FLAGS_MASK (DESC_COMMITTED_MASK | DESC_REUSE_MASK)
-#define DESC_ID_MASK (~DESC_FLAGS_MASK)
-
/* convenience struct for passing many values to helper functions */
struct prb_map {
char *prb;
@@ -21,12 +15,51 @@ struct prb_map {
char *text_data;
};
+/*
+ * desc_state and DESC_* definitions taken from kernel source:
+ *
+ * kernel/printk/printk_ringbuffer.h
+ */
+
+/* The possible responses of a descriptor state-query. */
+enum desc_state {
+ desc_miss = -1, /* ID mismatch (pseudo state) */
+ desc_reserved = 0x0, /* reserved, in use by writer */
+ desc_committed = 0x1, /* committed by writer, could get reopened */
+ desc_finalized = 0x2, /* committed, no further modification allowed */
+ desc_reusable = 0x3, /* free, not yet used by any writer */
+};
+
+#define DESC_SV_BITS (sizeof(unsigned long) * 8)
+#define DESC_FLAGS_SHIFT (DESC_SV_BITS - 2)
+#define DESC_FLAGS_MASK (3UL << DESC_FLAGS_SHIFT)
+#define DESC_STATE(sv) (3UL & (sv >> DESC_FLAGS_SHIFT))
+#define DESC_ID_MASK (~DESC_FLAGS_MASK)
+#define DESC_ID(sv) ((sv) & DESC_ID_MASK)
+
+/*
+ * get_desc_state() taken from kernel source:
+ *
+ * kernel/printk/printk_ringbuffer.c
+ */
+
+/* Query the state of a descriptor. */
+static enum desc_state get_desc_state(unsigned long id,
+ unsigned long state_val)
+{
+ if (id != DESC_ID(state_val))
+ return desc_miss;
+
+ return DESC_STATE(state_val);
+}
+
static void
dump_record(struct prb_map *m, unsigned long id)
{
unsigned long long ts_nsec;
unsigned long state_var;
unsigned short text_len;
+ enum desc_state state;
unsigned long begin;
unsigned long next;
char buf[BUFSIZE];
@@ -45,7 +78,8 @@ dump_record(struct prb_map *m, unsigned long id)
/* skip non-committed record */
state_var = ULONG(desc + OFFSET(prb_desc.state_var) + OFFSET(atomic_long_t.counter));
- if ((state_var & DESC_FLAGS_MASK) != DESC_COMMITTED_MASK)
+ state = get_desc_state(id, state_var);
+ if (state != desc_committed && state != desc_finalized)
return;
begin = ULONG(desc + OFFSET(prb_desc.text_blk_lpos) + OFFSET(prb_data_blk_lpos.begin)) %
--
2.20.1
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