101 lines
3.2 KiB
Diff
101 lines
3.2 KiB
Diff
From 71e159c64000467e94e08aefc144f5e1cdaa4aa0 Mon Sep 17 00:00:00 2001
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From: John Ogness <john.ogness@linutronix.de>
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Date: Wed, 25 Nov 2020 05:27:53 +0106
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Subject: [PATCH 2/2] printk: use committed/finalized state values
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An addendum to the previous crash commit a5531b24750e.
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The ringbuffer entries use 2 state values (committed and finalized)
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rather than a single flag to represent being available for reading.
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Copy the definitions and state lookup function directly from the
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kernel source and use the new states.
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Signed-off-by: John Ogness <john.ogness@linutronix.de>
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Signed-off-by: Nikolay Borisov <nborisov@suse.com>
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---
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printk.c | 48 +++++++++++++++++++++++++++++++++++++++++-------
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1 file changed, 41 insertions(+), 7 deletions(-)
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diff --git a/printk.c b/printk.c
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index f6d54ce9d0d8..8658016e65bf 100644
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--- a/printk.c
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+++ b/printk.c
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@@ -1,12 +1,6 @@
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#include "defs.h"
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#include <ctype.h>
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-#define DESC_SV_BITS (sizeof(unsigned long) * 8)
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-#define DESC_COMMITTED_MASK (1UL << (DESC_SV_BITS - 1))
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-#define DESC_REUSE_MASK (1UL << (DESC_SV_BITS - 2))
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-#define DESC_FLAGS_MASK (DESC_COMMITTED_MASK | DESC_REUSE_MASK)
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-#define DESC_ID_MASK (~DESC_FLAGS_MASK)
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-
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/* convenience struct for passing many values to helper functions */
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struct prb_map {
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char *prb;
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@@ -21,6 +15,44 @@ struct prb_map {
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char *text_data;
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};
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+/*
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+ * desc_state and DESC_* definitions taken from kernel source:
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+ *
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+ * kernel/printk/printk_ringbuffer.h
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+ */
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+
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+/* The possible responses of a descriptor state-query. */
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+enum desc_state {
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+ desc_miss = -1, /* ID mismatch (pseudo state) */
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+ desc_reserved = 0x0, /* reserved, in use by writer */
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+ desc_committed = 0x1, /* committed by writer, could get reopened */
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+ desc_finalized = 0x2, /* committed, no further modification allowed */
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+ desc_reusable = 0x3, /* free, not yet used by any writer */
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+};
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+
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+#define DESC_SV_BITS (sizeof(unsigned long) * 8)
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+#define DESC_FLAGS_SHIFT (DESC_SV_BITS - 2)
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+#define DESC_FLAGS_MASK (3UL << DESC_FLAGS_SHIFT)
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+#define DESC_STATE(sv) (3UL & (sv >> DESC_FLAGS_SHIFT))
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+#define DESC_ID_MASK (~DESC_FLAGS_MASK)
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+#define DESC_ID(sv) ((sv) & DESC_ID_MASK)
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+
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+/*
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+ * get_desc_state() taken from kernel source:
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+ *
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+ * kernel/printk/printk_ringbuffer.c
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+ */
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+
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+/* Query the state of a descriptor. */
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+static enum desc_state get_desc_state(unsigned long id,
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+ unsigned long state_val)
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+{
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+ if (id != DESC_ID(state_val))
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+ return desc_miss;
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+
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+ return DESC_STATE(state_val);
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+}
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+
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static void
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init_offsets(void)
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{
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@@ -74,6 +106,7 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags)
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unsigned short text_len;
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unsigned long state_var;
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unsigned int caller_id;
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+ enum desc_state state;
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unsigned char level;
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unsigned long begin;
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unsigned long next;
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@@ -90,7 +123,8 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags)
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/* skip non-committed record */
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state_var = ULONG(desc + OFFSET(prb_desc_state_var) +
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OFFSET(atomic_long_t_counter));
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- if ((state_var & DESC_FLAGS_MASK) != DESC_COMMITTED_MASK)
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+ state = get_desc_state(id, state_var);
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+ if (state != desc_committed && state != desc_finalized)
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return;
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info = m->infos + ((id % m->desc_ring_count) * SIZE(printk_info));
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--
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2.17.1
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