On 2022-07-25, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > I remember asking why it is needed to disable interrupts across > vsnprintf(). John, can I take this as-it or are you sending a new > batch? Mike's patch only addresses the vsnprintf() to print the prefix and get the message length. There is also a vscnprintf() for the message itself, which is still happening with interrupts disabled (see printk_sprint()). I suppose this patch side-steps the splat because the first vsnprintf() already triggered the random bytes for the pointer hash. I am preparing a new series that addresses this by completely removing interrupt disabling from the printk() path. This required changes to the printk_enter() macro, recursion handling, and the printk-ringbuffer itself. The focus of my new series are the various non-RT issues reported during the early 5.19-rc cycles. I still need more time to get the series into shape for LKML. If Mike's patch is reliably side-stepping the issue, feel free to take it. >> Bandaid: >> >> printk: fix RT vprintk_store() might sleep splat >> >> RT can't call vsnprintf() with IRQs disabled, so disable migration >> and move the printk_enter_irqsave() call down to where it's needed. It might be worth mentioning that vscnprintf() is called later in vprintk_store() when interrupts are disabled, but since it is s-printing the same string (and probably the same values), new random bytes are not required. (But someone should verify the reasoning here. I am not really familiar with the crng code.) John Ogness
