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Subject[PATCH] printk/nmi: avoid direct printk()-s from __printk_nmi_flush()
Date
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>

__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(), which takes care of in_nmi(), and use
it in __printk_nmi_flush() for printing and error-reporting.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
kernel/printk/nmi.c | 29 ++++++++++++++++++++---------
1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c
index b69eb8a..5f2c198 100644
--- a/kernel/printk/nmi.c
+++ b/kernel/printk/nmi.c
@@ -103,23 +103,32 @@ again:
* 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 __print_nmi_seq_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 print_nmi_seq_line(struct nmi_seq_buf *s, int start, int end)
+{
+ const char *buf = s->buffer + start;
+
+ __print_nmi_seq_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 +159,11 @@ 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";
+
+ __print_nmi_seq_line(msg, strlen(msg));
+ }

if (!len)
goto out; /* Someone else has already flushed the buffer. */
@@ -173,7 +184,7 @@ more:
/* Check if there was a partial line. */
if (last_i < size) {
print_nmi_seq_line(s, last_i, size - 1);
- pr_cont("\n");
+ __print_nmi_seq_line("\n", strlen("\n"));
}

/*
--
2.9.3
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