On Tue 2020-09-22 17:44:16, John Ogness wrote: > Since the ringbuffer is now lockless, new records can be inserted > directly from NMI context. There is no need for the NMI safe > buffers. Handle all NMI printk() calls using defer_console_output() > to avoid calling console drivers that might have their own locks. > > Signed-off-by: John Ogness <[email protected]> > --- > kernel/printk/printk_safe.c | 47 ++++--------------------------------- > 1 file changed, 4 insertions(+), 43 deletions(-) > > diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c > index 7c186cefdb50..720935d19a3e 100644 > --- a/kernel/printk/printk_safe.c > +++ b/kernel/printk/printk_safe.c > @@ -355,10 +324,11 @@ __printf(1, 0) int vprintk_func(const char *fmt, > va_list args) > #endif > > /* > - * Try to use the main logbuf even in NMI. But avoid calling console > + * Use the main ringbuffer in NMI. But avoid calling console > * drivers that might have their own locks. > */ > - if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK)) { > + if ((this_cpu_read(printk_context) & > + (PRINTK_NMI_CONTEXT_MASK | PRINTK_NMI_DIRECT_CONTEXT_MASK))) { > int len; > > len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args); > @@ -366,10 +336,6 @@ __printf(1, 0) int vprintk_func(const char *fmt, va_list > args) > return len; > } > > - /* Use extra buffer in NMI. */ > - if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK) > - return vprintk_nmi(fmt, args); > - > /* Use extra buffer to prevent a recursion deadlock in safe mode. */ > if (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK) > return vprintk_safe(fmt, args);
I still hope that we will be able to get rid of printk_safe completely. I would expect that only two situations would need special handling with the lockless ringbuffer: + call vkdb_printf() in kdb context + defer console in NMI context Eventually we should prevent too big level of recursion. Best Regards, Petr
