On 2021-10-29, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > ftrace_dump() is used for instance by alt-sysrq-z / sysrq_ftrace_dump(). > The function itself dumps the whole trace buffer in an irq-off section so > no need to talk about max latencies unless this is going to change. > > The output on the serial is more or less brief and starts with > "** 397774 printk messages dropped **" > and so I do see only the end of it. Might be okay. > Any reason not to use the sync mode + atomic console while ftrace_dump() > is in progress? Since latencies are not a concern, I see no reason not to use sync+atomic. However, it does put us into the situation of beginning to define non-emergency scenarios where sync+atomic is used. That rabbit hole might go quite deep. I wonder if it might be better to introduce a new sysrq to toggle sync mode. John
