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authorJohn Ogness <john.ogness@linutronix.de>2020-12-09 01:50:53 +0106
committerPetr Mladek <pmladek@suse.com>2020-12-09 11:31:02 +0100
commitb031a684bfd01d633c79d281bd0cf11c2f834ada (patch)
treeca2ab9169fe3eba5a846f4cc02cef15395d55317 /init
parent6b916706f8f09348cfa4fdd3642ebf87d6a2a26b (diff)
downloadlinux-b031a684bfd01d633c79d281bd0cf11c2f834ada.tar.bz2
printk: remove logbuf_lock writer-protection of ringbuffer
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 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 <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20201209004453.17720-3-john.ogness@linutronix.de
Diffstat (limited to 'init')
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