The patch titled
Subject: printk/nmi: avoid direct printk()-s from __printk_nmi_flush()
has been added to the -mm tree. Its filename is
printk-nmi-avoid-direct-printk-s-from-__printk_nmi_flush.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/printk-nmi-avoid-direct-printk-s-from-__printk_nmi_flush.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/printk-nmi-avoid-direct-printk-s-from-__printk_nmi_flush.patch
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------------------------------------------------------
From: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Subject: printk/nmi: avoid direct printk()-s from __printk_nmi_flush()
__printk_nmi_flush() can be called from nmi_panic(), therefore it has to
test whether it's executed in NMI context and thus must route the messages
through deferred printk() or via direct printk(). Except for two places
where __printk_nmi_flush() does unconditional direct printk() calls:
- pr_err("printk_nmi_flush: internal error ...")
- pr_cont("\n")
Factor out print_nmi_seq_line() parts into a new printk_nmi_flush_line()
function, which takes care of in_nmi(), and use it in __printk_nmi_flush()
for printing and error-reporting.
Link: http://lkml.kernel.org/r/20160830161354.581-1-sergey.senozhatsky@xxxxxxxxx
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/printk/nmi.c | 38 +++++++++++++++++++++++---------------
1 file changed, 23 insertions(+), 15 deletions(-)
diff -puN kernel/printk/nmi.c~printk-nmi-avoid-direct-printk-s-from-__printk_nmi_flush kernel/printk/nmi.c
--- a/kernel/printk/nmi.c~printk-nmi-avoid-direct-printk-s-from-__printk_nmi_flush
+++ a/kernel/printk/nmi.c
@@ -99,27 +99,33 @@ again:
return add;
}
-/*
- * printk one line from the temporary buffer from @start index until
- * and including the @end index.
- */
-static void print_nmi_seq_line(struct nmi_seq_buf *s, int start, int end)
+static void printk_nmi_flush_line(const char *text, int len)
{
- const char *buf = s->buffer + start;
-
/*
* The buffers are flushed in NMI only on panic. The messages must
* go only into the ring buffer at this stage. Consoles will get
* explicitly called later when a crashdump is not generated.
*/
if (in_nmi())
- printk_deferred("%.*s", (end - start) + 1, buf);
+ printk_deferred("%.*s", len, text);
else
- printk("%.*s", (end - start) + 1, buf);
+ printk("%.*s", len, text);
}
/*
+ * printk one line from the temporary buffer from @start index until
+ * and including the @end index.
+ */
+static void printk_nmi_flush_seq_line(struct nmi_seq_buf *s,
+ int start, int end)
+{
+ const char *buf = s->buffer + start;
+
+ printk_nmi_flush_line(buf, (end - start) + 1);
+}
+
+/*
* Flush data from the associated per_CPU buffer. The function
* can be called either via IRQ work or independently.
*/
@@ -150,9 +156,11 @@ more:
* the buffer an unexpected way. If we printed something then
* @len must only increase.
*/
- if (i && i >= len)
- pr_err("printk_nmi_flush: internal error: i=%d >= len=%zu\n",
- i, len);
+ if (i && i >= len) {
+ const char *msg = "printk_nmi_flush: internal error\n";
+
+ printk_nmi_flush_line(msg, strlen(msg));
+ }
if (!len)
goto out; /* Someone else has already flushed the buffer. */
@@ -166,14 +174,14 @@ more:
/* Print line by line. */
for (; i < size; i++) {
if (s->buffer[i] == '\n') {
- print_nmi_seq_line(s, last_i, i);
+ printk_nmi_flush_seq_line(s, last_i, i);
last_i = i + 1;
}
}
/* Check if there was a partial line. */
if (last_i < size) {
- print_nmi_seq_line(s, last_i, size - 1);
- pr_cont("\n");
+ printk_nmi_flush_seq_line(s, last_i, size - 1);
+ printk_nmi_flush_line("\n", strlen("\n"));
}
/*
_
Patches currently in -mm which might be from sergey.senozhatsky.work@xxxxxxxxx are
printk-nmi-avoid-direct-printk-s-from-__printk_nmi_flush.patch
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