The /dev/kmsg can return EPIPE if current record has beed modified
while reading.
For init_kmsg, it cause switch to DMESG_METHOD_SYSLOG
(which is not expected) and later it can truncate output.
Signed-off-by: Milan Broz <mbroz@xxxxxxxxxx>
---
sys-utils/dmesg.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/sys-utils/dmesg.c b/sys-utils/dmesg.c
index e92904f..0ee03ee 100644
--- a/sys-utils/dmesg.c
+++ b/sys-utils/dmesg.c
@@ -851,6 +851,19 @@ static void print_buffer(struct dmesg_control *ctl,
print_record(ctl, &rec);
}
+static ssize_t read_kmsg_one(struct dmesg_control *ctl)
+{
+ ssize_t size;
+
+ /* kmsg returns EPIPE if record was modified while reading */
+ do {
+ size = read(ctl->kmsg, ctl->kmsg_buf,
+ sizeof(ctl->kmsg_buf) - 1);
+ } while (size < 0 && errno == EPIPE);
+
+ return size;
+}
+
static int init_kmsg(struct dmesg_control *ctl)
{
int mode = O_RDONLY;
@@ -877,8 +890,7 @@ static int init_kmsg(struct dmesg_control *ctl)
* Let's try to read the first record. The record is later processed in
* read_kmsg().
*/
- ctl->kmsg_first_read = read(ctl->kmsg, ctl->kmsg_buf,
- sizeof(ctl->kmsg_buf) - 1);
+ ctl->kmsg_first_read = read_kmsg_one(ctl);
if (ctl->kmsg_first_read < 0) {
close(ctl->kmsg);
ctl->kmsg = -1;
@@ -996,7 +1008,7 @@ static int read_kmsg(struct dmesg_control *ctl)
ctl->kmsg_buf, (size_t) sz) == 0)
print_record(ctl, &rec);
- sz = read(ctl->kmsg, ctl->kmsg_buf, sizeof(ctl->kmsg_buf) - 1);
+ sz = read_kmsg_one(ctl);
}
return 0;
--
1.7.10.4
--
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