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    SubjectRe: [RFC 3/8] kmsg: introduce additional kmsg devices support
    On Fri 2015-07-03 12:49:50, Marcin Niesluchowski wrote:
    > kmsg device provides operations on cyclic logging buffer used mainly
    > by kernel but also in userspace by privileged processes.
    >
    > Additional kmsg devices keep the same log format but may be added
    > dynamically with custom size.
    >
    > Signed-off-by: Marcin Niesluchowski <m.niesluchow@samsung.com>

    > --- a/kernel/printk/printk.c
    > +++ b/kernel/printk/printk.c
    > @@ -234,29 +234,37 @@ struct printk_log {
    > u8 level:3; /* syslog level */
    > };

    Just in case, this is accepted. If you already touch the API, I would
    suggest to rename struct printk_log to printk_msg. The current name
    is pretty misleading.

    > +struct log_buffer {
    > +#ifdef CONFIG_PRINTK
    > + struct list_head list; /* kmsg as head of the list */
    > + char *buf; /* cyclic log buffer */
    > + u32 len; /* buffer length */
    > + wait_queue_head_t wait; /* wait queue for kmsg buffer */
    > +#endif
    > /*
    > - * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
    > - * within the scheduler's rq lock. It must be released before calling
    > - * console_unlock() or anything else that might wake up a process.
    > + * The lock protects kmsg buffer, indices, counters. This can be taken within
    > + * the scheduler's rq lock. It must be released before calling console_unlock()
    > + * or anything else that might wake up a process.
    > */
    > -static DEFINE_RAW_SPINLOCK(logbuf_lock);
    > + raw_spinlock_t lock;
    > + u64 first_seq; /* sequence number of the first record stored */
    > + u32 first_idx; /* index of the first record stored */
    > +/* sequence number of the next record to store */
    > + u64 next_seq;
    > +#ifdef CONFIG_PRINTK
    > + u32 next_idx; /* index of the next record to store */
    > + int mode; /* mode of device (kmsg_sys only) */
    > + int minor; /* minor representing buffer device */
    > +#endif
    > +};


    > @@ -1069,10 +1253,10 @@ const struct file_operations kmsg_fops = {
    > */
    > void log_buf_kexec_setup(void)
    > {
    > - VMCOREINFO_SYMBOL(log_buf);
    > - VMCOREINFO_SYMBOL(log_buf_len);
    > - VMCOREINFO_SYMBOL(log_first_idx);
    > - VMCOREINFO_SYMBOL(log_next_idx);
    > + VMCOREINFO_SYMBOL(log_buf.buf);
    > + VMCOREINFO_SYMBOL(log_buf.len);
    > + VMCOREINFO_SYMBOL(log_buf.first_idx);
    > + VMCOREINFO_SYMBOL(log_buf.next_idx);

    Have you tried to use this in crash or some other utility, please?
    I guess that it will need to be exported a similar way like
    struct printk_log, something like:

    VMCOREINFO_SYMBOL(log_buf);
    VMCOREINFO_STRUCT_SIZE(log_buffer);
    VMCOREINFO_OFFSET(log_buffer, buf);
    VMCOREINFO_OFFSET(log_buffer, len);
    VMCOREINFO_OFFSET(log_buffer, first_idx);
    VMCOREINFO_OFFSET(log_buffer, next_idx);

    Best Regards,
    Petr


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