Hi, Here is v4 of a series to remove the safe buffers. v3 can be found here [0]. The safe buffers are no longer needed because messages can be stored directly into the log buffer from any context. However, the safe buffers also provided a form of recursion protection. For that reason, explicit recursion protection is implemented for this series. The safe buffers also implicitly provided serialization between multiple CPUs executing in NMI context. This was particularly necessary for the nmi_backtrace() output. This serializiation is now preserved by using the printk cpulock. With the removal of the safe buffers, there is no need for extra NMI enter/exit tracking. So this is also removed (which includes removing the config option CONFIG_PRINTK_NMI). And finally, there are a few places in the kernel that need to specify code blocks where all printk calls are to be deferred printing. Previously the NMI tracking API was being (mis)used for this purpose. This series introduces an official and explicit interface for such cases. (Note that all deferred printing will be removed anyway, once printing kthreads are introduced.) Changes since v3: - Remove safe context tracking in vprintk(). - Add safe context tracking for @console_owner usage since that is also a component of the printing code. - Refactor syslog_print() so that it is easier to understand and follow the locking logic. - Introduce printk_deferred_enter/exit functions to be used by code that needs to specify code block where all printk calls are to be deferred printing. John Ogness [0] https://lore.kernel.org/lkml/20210624111148.5190-1-john.ogness@xxxxxxxxxxxxx John Ogness (6): lib/nmi_backtrace: explicitly serialize banner and regs printk: track/limit recursion printk: remove safe buffers printk: remove NMI tracking printk: convert @syslog_lock to mutex printk: syslog: close window between wait and read arch/arm/kernel/smp.c | 4 +- arch/powerpc/kernel/traps.c | 1 - arch/powerpc/kernel/watchdog.c | 5 - arch/powerpc/kexec/crash.c | 2 +- include/linux/hardirq.h | 2 - include/linux/printk.h | 41 ++-- init/Kconfig | 5 - kernel/kexec_core.c | 1 - kernel/panic.c | 3 - kernel/printk/internal.h | 25 --- kernel/printk/printk.c | 268 ++++++++++++++---------- kernel/printk/printk_safe.c | 364 +-------------------------------- kernel/trace/trace.c | 4 +- lib/nmi_backtrace.c | 13 +- 14 files changed, 194 insertions(+), 544 deletions(-) base-commit: 70333dec446292cd896cd051d2ebd6808b328949 -- 2.20.1 _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
