en Copyright 2015 Java http://kernelsources.org:8080/source/history/linux/arch/arm64/include/asm/ring_buffer.h#7acfa2c5f4366d63653380646ffa7dbd1bfaccc0 Merge tag 'trace-ringbuffer-v7.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracePull ring-buffer fixes from Steven Rostedt: - Fix reporting MISSED EVENTS in trace iterator When the "trace" file is read with tracing enabled, if the writer were to pass the iterator reader, it resets, sets a "missed_events" flag and continues. The tracing output checks for missed events and if there are some, it prints out "[LOST EVENTS]" to let the user know events were dropped. But the clearing of the missed_events happened when the tracing system queried the ring buffer iterator about missed events. This was premature as the ring buffer is per CPU, and the tracing code reads all the CPU buffers and checks for missed events when it is read. If the CPU iterator that had missed events isn't printed next, the output for the LOST EVENTS is lost. Clear the missed_events flag when the iterator moves to the next event and not when the missed_events flag is queried. Also clear it on reset. - Flush and stop the persistent ring buffer on panic On panic the persistent ring buffer is used to debug what caused the panic. But on some architectures, it requires flushing the memory from cache, otherwise, the ring buffer persistent memory may not have the last events and this could also cause the ring buffer to be corrupted on the next boot. - Fix nr_subbufs initialization in simple_ring_buffer_init_mm The remote simple ring buffer meta data nr_subbufs is initialized too early and gets cleared later on, making it zero and not reflect the actual number of sub-buffers. - Fix unload_page for simple_ring_buffer init rollback On error, the pages loaded need to be unloaded. To unload a page it is expected that: page = load_page(va); -> unload_page(page). But the code was doing: unload_page(va) and not unload_page(page). - Create output file from cmd_check_undefined The check for undefined symbols checks if the file *.o.checked exists and if so it skips doing the work. But the *.o.checked file never was created making every build do the work even when it was already done previously.* tag 'trace-ringbuffer-v7.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing: Create output file from cmd_check_undefined tracing: Fix unload_page for simple_ring_buffer init rollback tracing: Fix nr_subbufs initialization in simple_ring_buffer_init_mm() ring-buffer: Flush and stop persistent ring buffer on panic ring-buffer: Fix reporting of missed events in iterator List of files: /linux/arch/arm64/include/asm/ring_buffer.h Thu, 21 May 2026 23:05:09 +0200 Linus Torvalds <torvalds@linux-foundation.org> http://kernelsources.org:8080/source/history/linux/arch/arm64/include/asm/ring_buffer.h#a494d3c8d5392bcdff83c2a593df0c160ff9f322 ring-buffer: Flush and stop persistent ring buffer on panicOn real hardware, panic and machine reboot may not flush hardware cacheto memory. This means the persistent ring buffer, which relies on acoherent state of memory, may not have its events written to the bufferand they may be lost. Moreover, there may be inconsistency with thecounters which are used for validation of the integrity of thepersistent ring buffer which may cause all data to be discarded.To avoid this issue, stop recording of the ring buffer on panic andflush the cache of the ring buffer's memory.Fixes: e645535a954a ("tracing: Add option to use memmapped memory for trace boot instance")Cc: stable@vger.kernel.orgCc: Will Deacon <will@kernel.org>Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>Cc: Ian Rogers <irogers@google.com>Link: https://patch.msgid.link/177751969602.2136606.12031934362587643488.stgit@mhiramat.tok.corp.google.comSigned-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>Acked-by: Catalin Marinas <catalin.marinas@arm.com>Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>Signed-off-by: Steven Rostedt <rostedt@goodmis.org> List of files: /linux/arch/arm64/include/asm/ring_buffer.h Thu, 30 Apr 2026 05:28:16 +0200 Masami Hiramatsu (Google) <mhiramat@kernel.org>