On Sat 2019-02-16 19:59:33, Tetsuo Handa wrote:
> When thread1 called printk() which did not end with '\n', and then thread2
> called printk() which ends with '\n' before thread1 calls pr_cont(), the
> partial content saved into "struct cont" is flushed by thread2 despite the
> partial content was generated by thread1. This leads to confusing output
> as if the partial content was generated by thread2. Fix this problem by
> passing correct caller information to log_store().
>
> Before:
>
> [ T8533] abcdefghijklm
> [ T8533] ABCDEFGHIJKLMNOPQRSTUVWXYZ
> [ T8532] nopqrstuvwxyz
> [ T8532] abcdefghijklmnopqrstuvwxyz
> [ T8533] abcdefghijklm
> [ T8533] ABCDEFGHIJKLMNOPQRSTUVWXYZ
> [ T8532] nopqrstuvwxyz
>
> After:
>
> [ T8507] abcdefghijklm
> [ T8508] ABCDEFGHIJKLMNOPQRSTUVWXYZ
> [ T8507] nopqrstuvwxyz
> [ T8507] abcdefghijklmnopqrstuvwxyz
> [ T8507] abcdefghijklm
> [ T8508] ABCDEFGHIJKLMNOPQRSTUVWXYZ
> [ T8507] nopqrstuvwxyz
Great catch!
> Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
The patch looks fine to me:
Reviewed-by: Petr Mladek <pmla...@suse.com>
There are just two cosmetic changes that I might do when pushing
the patch, see below.
> ---
> kernel/printk/printk.c | 39 ++++++++++++++++++++++++---------------
> 1 file changed, 24 insertions(+), 15 deletions(-)
>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 33c0359..6547a88 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1850,13 +1854,16 @@ static bool cont_add(int facility, int level, enum
> log_flags flags, const char *
>
> static size_t log_output(int facility, int level, enum log_flags lflags,
> const char *dict, size_t dictlen, char *text, size_t text_len)
> {
> + const u32 caller_id = printk_caller_id();
> +
> /*
> * If an earlier line was buffered, and we're a continuation
> - * write from the same process, try to add it to the buffer.
> + * write from the same context, try to add it to the buffer.
> */
> if (cont.len) {
> - if (cont.owner == current && (lflags & LOG_CONT)) {
> - if (cont_add(facility, level, lflags, text, text_len))
> + if (cont.caller_id == caller_id && (lflags & LOG_CONT)) {
> + if (cont_add(caller_id, facility, level, lflags, text,
> + text_len))
I think that this is the case when it is better to break the 80-character
per-line rule.
> return text_len;
> }
> /* Otherwise, make sure it's flushed */
> @@ -1869,12 +1876,14 @@ static size_t log_output(int facility, int level,
> enum log_flags lflags, const c
>
> /* If it doesn't end in a newline, try to buffer the current line */
> if (!(lflags & LOG_NEWLINE)) {
> - if (cont_add(facility, level, lflags, text, text_len))
> + if (cont_add(caller_id, facility, level, lflags, text,
> + text_len))
Same here.
> return text_len;
> }
>
Best Regards,
Petr
