On Wed, 2012-11-28 at 17:49 +0100, Kay Sievers wrote:
> On Wed, Nov 28, 2012 at 5:37 PM, Linus Torvalds
> <torva...@linux-foundation.org> wrote:
> > On Wed, Nov 28, 2012 at 8:22 AM, Kay Sievers <k...@vrfy.org> wrote:
> >> On Wed, Nov 28, 2012 at 2:33 PM, Michael Kerrisk <mtk.manpa...@gmail.com>
> >> wrote:
> >>
> >>> On a 2.6.31 system, immediately after SYSLOG_ACTION_READ_CLEAR, a
> >>> SYSLOG_ACTION_SIZE_UNREAD returns 0.
> >>
> >> Hmm, sounds like the right thing to do.
> >
> > Right.
> >
> > And that's the *OLD* behavior (2.6.31).
>
> Ah, hmm, I read 2.6... as 3.6... :)
>
> > So the new behavior is insane and different. Let's fix it.
>
> Yeah.
>
> > It looks like it is because the new SYSLOG_ACTION_SIZE_UNREAD code
> > does not take the new clear_seq code into account. Hmm?
>
> Right, something like that. I'll take a look now ...
From: Kay Sievers <k...@vrfy.org>
Subject: printk: respect SYSLOG_ACTION_READ_CLEAR for SYSLOG_ACTION_SIZE_UNREAD
On Wed, Nov 28, 2012 at 2:33 PM, Michael Kerrisk <mtk.manpa...@gmail.com> wrote:
> It looks as though the changes here have broken SYSLOG_ACTION_SIZE_UNREAD.
>
> On a 2.6.31 system, immediately after SYSLOG_ACTION_READ_CLEAR, a
> SYSLOG_ACTION_SIZE_UNREAD returns 0.
>
> On 3.5, immediately after SYSLOG_ACTION_READ_CLEAR, the value returned
> by SYSLOG_ACTION_SIZE_UNREAD is unchanged (i.e., assuming that the
> value returned was non-zero before SYSLOG_ACTION_SIZE_UNREAD, it is
> still nonzero afterward), even though a subsequent
> SYSLOG_ACTION_READ_CLEAR indicates that there are zero bytes to read.
Fix SYSLOG_ACTION_SIZE_UNREAD to return the amount of available
characters by starting to count at the first available record after
the last SYSLOG_ACTION_READ_CLEAR, instead of the first message
record for SYSLOG_ACTION_READ.
Before:
syslog(SYSLOG_ACTION_SIZE_UNREAD, 0, 0) = 286965
syslog(SYSLOG_ACTION_READ_CLEAR, "<12>"..., 1000000) = 24000
syslog(SYSLOG_ACTION_SIZE_UNREAD, 0, 0) = 286965
After:
syslog(SYSLOG_ACTION_SIZE_UNREAD, 0, 0) = 90402
syslog(SYSLOG_ACTION_READ_CLEAR, "<5>"..., 1000000) = 90402
syslog(SYSLOG_ACTION_SIZE_UNREAD, 0, 0) = 0
Reported-By: Michael Kerrisk <mtk.manpa...@gmail.com>
Signed-Off-By: Kay Sievers <k...@vrfy.org>
---
printk.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index 2d607f4..35a7f4f 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1183,12 +1183,10 @@ int do_syslog(int type, char __user *buf, int len, bool
from_file)
/* Number of chars in the log buffer */
case SYSLOG_ACTION_SIZE_UNREAD:
raw_spin_lock_irq(&logbuf_lock);
- if (syslog_seq < log_first_seq) {
+ if (clear_seq < log_first_seq) {
/* messages are gone, move to first one */
- syslog_seq = log_first_seq;
- syslog_idx = log_first_idx;
- syslog_prev = 0;
- syslog_partial = 0;
+ clear_seq = log_first_seq;
+ clear_idx = log_first_idx;
}
if (from_file) {
/*
@@ -1198,9 +1196,9 @@ int do_syslog(int type, char __user *buf, int len, bool
from_file)
*/
error = log_next_idx - syslog_idx;
} else {
- u64 seq = syslog_seq;
- u32 idx = syslog_idx;
- enum log_flags prev = syslog_prev;
+ u64 seq = clear_seq;
+ u32 idx = clear_idx;
+ enum log_flags prev = 0;
error = 0;
while (seq < log_next_seq) {
@@ -1211,7 +1209,6 @@ int do_syslog(int type, char __user *buf, int len, bool
from_file)
seq++;
prev = msg->flags;
}
- error -= syslog_partial;
}
raw_spin_unlock_irq(&logbuf_lock);
break;
--
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