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0161e2d695
The documentation of printk_cpu_sync_get() clearly states that the owner must never perform any activities where it waits for a CPU. For legacy printing there can be spinning on the console_lock and on the port lock. Therefore legacy printing must be deferred when holding the printk_cpu_sync. Note that in the case of emergency states, atomic consoles are not prevented from printing when printk is deferred. This is appropriate because they do not spin-wait indefinitely for other CPUs. Reported-by: Rik van Riel <riel@surriel.com> Closes: https://lore.kernel.org/r/20240715232052.73eb7fb1@imladris.surriel.com Signed-off-by: John Ogness <john.ogness@linutronix.de> Fixes: 55d6af1d6688 ("lib/nmi_backtrace: explicitly serialize banner and regs") Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20241209111746.192559-3-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com>