Hello, Here is v2 for the second series to rework the printk subsystem. (The v1 is here [0].) This series implements a new ringbuffer feature that allows the last record to be extended. Petr Mladek provided the initial proof of concept [1] for this. Using the record extension feature, LOG_CONT is re-implemented in a way that exactly preserves its behavior, but avoids the need for an extra buffer. In particular, it avoids the need for any synchronization that such a buffer requires. This series deviates from the agreements [2] made at the meeting during LPC2019 in Lisbon. The test results of the v1 series showed that the effects on existing userspace tools using /dev/kmsg (journalctl, dmesg) were not acceptable [3]. That is why a new decision [4] was made to preserve the current LOG_CONT behavior. Patch 5 introduces two new memory barriers. However, both are alternate path memory barriers. They exactly match the purpose and context of the two existing memory barriers that they provide an alternate path for. For this reason, I do not believe that a new memory barrier review is necessary. Nevertheless, I have included the memory barrier experts CC. Patch 6 assumes that the gdb script series [5] for the new printk ringbuffer has been applied. John Ogness [0] https://lkml.kernel.org/r/20200717234818.8622-1-john.ogness@xxxxxxxxxxxxx [1] https://lkml.kernel.org/r/20200812163908.GH12903@alley [2] https://lkml.kernel.org/r/87k1acz5rx.fsf@xxxxxxxxxxxxx [3] https://lkml.kernel.org/r/20200811160551.GC12903@alley [4] https://lkml.kernel.org/r/CAHk-=wj_b6Bh=d-Wwh0xYqoQBhHkYeExhszkpxdRA6GjTvkRiQ@xxxxxxxxxxxxxx [5] https://lkml.kernel.org/r/20200814212525.6118-1-john.ogness@xxxxxxxxxxxxx John Ogness (7): printk: ringbuffer: rename DESC_COMMITTED_MASK flag printk: ringbuffer: change representation of reusable printk: ringbuffer: relocate get_data() printk: ringbuffer: add BLK_DATALESS() macro printk: ringbuffer: add finalization/extension support printk: reimplement log_cont using record extension scripts/gdb: support printk finalized records Documentation/admin-guide/kdump/gdbmacros.txt | 10 +- kernel/printk/printk.c | 98 +--- kernel/printk/printk_ringbuffer.c | 496 +++++++++++++++--- kernel/printk/printk_ringbuffer.h | 12 +- scripts/gdb/linux/dmesg.py | 10 +- 5 files changed, 453 insertions(+), 173 deletions(-) -- 2.20.1 _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
