On Wed 2020-12-09 01:50:53, John Ogness wrote: > Since the ringbuffer is lockless, there is no need for it to be > protected by @logbuf_lock. Remove @logbuf_lock writer-protection of > the ringbuffer. The reader-protection is not removed because some > some variables used by readers are using @logbuf_lock for > synchronization: @syslog_seq, @syslog_time, @syslog_partial, > @console_seq, struct kmsg_dumper. > > For PRINTK_NMI_DIRECT_CONTEXT_MASK, @logbuf_lock usage is not removed > because it may be used for dumper synchronization. > > Without @logbuf_lock synchronization of vprintk_store() it is no > longer possible to use the single static buffer for temporarily > sprint'ing the message. Instead, use vsnprintf() to determine the > length and perform the real vscnprintf() using the area reserved from > the ringbuffer. This leads to suboptimal packing of the message data, > but will result in less wasted storage than multiple per-cpu buffers > to support lockless temporary sprint'ing. > > Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]> Best Regards, Petr
