1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
|
From 44945f908f87501b711299bfe736012ed927526b Mon Sep 17 00:00:00 2001
From: John Ogness <john.ogness@linutronix.de>
Date: Mon, 30 Nov 2020 01:42:10 +0106
Subject: [PATCH 108/323] printk: add pr_flush()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.215-rt107.tar.xz
Provide a function to allow waiting for console printers to catch
up to the latest logged message.
Use pr_flush() to give console printers a chance to finish in
critical situations if no atomic console is available. For now
pr_flush() is only used in the most common error paths:
panic(), print_oops_end_marker(), report_bug(), kmsg_dump().
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
---
include/linux/printk.h | 2 ++
kernel/panic.c | 28 +++++++++------
kernel/printk/printk.c | 79 ++++++++++++++++++++++++++++++++++++++++++
lib/bug.c | 1 +
4 files changed, 99 insertions(+), 11 deletions(-)
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 410435ac15ea1..83c7734e98025 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -481,6 +481,8 @@ extern int kptr_restrict;
no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#endif
+bool pr_flush(int timeout_ms, bool reset_on_progress);
+
/*
* ratelimited messages with local ratelimit_state,
* no local ratelimit_state used in the !PRINTK case
diff --git a/kernel/panic.c b/kernel/panic.c
index 7fc35d3675e1b..0681472a2041a 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -244,6 +244,7 @@ void check_panic_on_warn(const char *origin)
void panic(const char *fmt, ...)
{
static char buf[1024];
+ va_list args2;
va_list args;
long i, i_next = 0, len;
int state = 0;
@@ -260,6 +261,21 @@ void panic(const char *fmt, ...)
panic_on_warn = 0;
}
+ console_verbose();
+ pr_emerg("Kernel panic - not syncing:\n");
+ va_start(args2, fmt);
+ va_copy(args, args2);
+ vprintk(fmt, args2);
+ va_end(args2);
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+ /*
+ * Avoid nested stack-dumping if a panic occurs during oops processing
+ */
+ if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
+ dump_stack();
+#endif
+ pr_flush(1000, true);
+
/*
* Disable local interrupts. This will prevent panic_smp_self_stop
* from deadlocking the first cpu that invokes the panic, since
@@ -290,24 +306,13 @@ void panic(const char *fmt, ...)
if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)
panic_smp_self_stop();
- console_verbose();
bust_spinlocks(1);
- va_start(args, fmt);
len = vscnprintf(buf, sizeof(buf), fmt, args);
va_end(args);
if (len && buf[len - 1] == '\n')
buf[len - 1] = '\0';
- pr_emerg("Kernel panic - not syncing: %s\n", buf);
-#ifdef CONFIG_DEBUG_BUGVERBOSE
- /*
- * Avoid nested stack-dumping if a panic occurs during oops processing
- */
- if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
- dump_stack();
-#endif
-
/*
* If kgdb is enabled, give it a chance to run before we stop all
* the other CPUs or else we won't be able to debug processes left
@@ -637,6 +642,7 @@ static void print_oops_end_marker(void)
{
init_oops_id();
pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
+ pr_flush(1000, true);
}
/*
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 0cc452e7b1a1c..3fdd06c05f4ea 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3256,6 +3256,12 @@ void kmsg_dump(enum kmsg_dump_reason reason)
sync_mode = true;
pr_info("enabled sync mode\n");
}
+
+ /*
+ * Give the printing threads time to flush, allowing up to
+ * 1s of no printing forward progress before giving up.
+ */
+ pr_flush(1000, true);
}
rcu_read_lock();
@@ -3535,3 +3541,76 @@ void console_atomic_unlock(unsigned int flags)
prb_unlock(&printk_cpulock, flags);
}
EXPORT_SYMBOL(console_atomic_unlock);
+
+static void pr_msleep(bool may_sleep, int ms)
+{
+ if (may_sleep) {
+ msleep(ms);
+ } else {
+ while (ms--)
+ udelay(1000);
+ }
+}
+
+/**
+ * pr_flush() - Wait for printing threads to catch up.
+ *
+ * @timeout_ms: The maximum time (in ms) to wait.
+ * @reset_on_progress: Reset the timeout if forward progress is seen.
+ *
+ * A value of 0 for @timeout_ms means no waiting will occur. A value of -1
+ * represents infinite waiting.
+ *
+ * If @reset_on_progress is true, the timeout will be reset whenever any
+ * printer has been seen to make some forward progress.
+ *
+ * Context: Any context.
+ * Return: true if all enabled printers are caught up.
+ */
+bool pr_flush(int timeout_ms, bool reset_on_progress)
+{
+ int remaining = timeout_ms;
+ struct console *con;
+ u64 last_diff = 0;
+ bool may_sleep;
+ u64 printk_seq;
+ u64 diff;
+ u64 seq;
+
+ may_sleep = (preemptible() && !in_softirq());
+
+ seq = prb_next_seq(prb);
+
+ for (;;) {
+ diff = 0;
+
+ for_each_console(con) {
+ if (!(con->flags & CON_ENABLED))
+ continue;
+ printk_seq = atomic64_read(&con->printk_seq);
+ if (printk_seq < seq)
+ diff += seq - printk_seq;
+ }
+
+ if (diff != last_diff && reset_on_progress)
+ remaining = timeout_ms;
+
+ if (!diff || remaining == 0)
+ break;
+
+ if (remaining < 0) {
+ pr_msleep(may_sleep, 100);
+ } else if (remaining < 100) {
+ pr_msleep(may_sleep, remaining);
+ remaining = 0;
+ } else {
+ pr_msleep(may_sleep, 100);
+ remaining -= 100;
+ }
+
+ last_diff = diff;
+ }
+
+ return (diff == 0);
+}
+EXPORT_SYMBOL(pr_flush);
diff --git a/lib/bug.c b/lib/bug.c
index 4ab398a2de938..9c681f29e61e6 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -202,6 +202,7 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
else
pr_crit("Kernel BUG at %pB [verbose debug info unavailable]\n",
(void *)bugaddr);
+ pr_flush(1000, true);
return BUG_TRAP_TYPE_BUG;
}
--
2.44.0
|
