From 8d58e99af5980d444948720977b0976455885391 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Thu, 19 Jun 2014 17:33:30 -0400 Subject: [PATCH] seq_buf: Move the seq_buf code to lib/ The seq_buf functions are rather useful outside of tracing. Instead of having it be dependent on CONFIG_TRACING, move the code into lib/ and allow other users to have access to it even when tracing is not configured. The seq_buf utility is similar to the seq_file utility, but instead of writing sending data back up to userland, it writes it into a buffer defined at seq_buf_init(). This allows us to send a descriptor around that writes printf() formatted strings into it that can be retrieved later. It is currently used by the tracing facility for such things like trace events to convert its binary saved data in the ring buffer into an ASCII human readable context to be displayed in /sys/kernel/debug/trace. It can also be used for doing NMI prints safely from NMI context into the seq_buf and retrieved later and dumped to printk() safely. Doing printk() from an NMI context is dangerous because an NMI can preempt a current printk() and deadlock on it. Link: http://lkml.kernel.org/p/20140619213952.058255809@goodmis.org Tested-by: Jiri Kosina Acked-by: Jiri Kosina Reviewed-by: Petr Mladek Signed-off-by: Steven Rostedt --- kernel/trace/Makefile | 1 - lib/Makefile | 2 +- {kernel/trace => lib}/seq_buf.c | 0 3 files changed, 1 insertion(+), 2 deletions(-) rename {kernel/trace => lib}/seq_buf.c (100%) diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index edc98c72a634..67d6369ddf83 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -29,7 +29,6 @@ obj-$(CONFIG_RING_BUFFER_BENCHMARK) += ring_buffer_benchmark.o obj-$(CONFIG_TRACING) += trace.o obj-$(CONFIG_TRACING) += trace_output.o obj-$(CONFIG_TRACING) += trace_seq.o -obj-$(CONFIG_TRACING) += seq_buf.o obj-$(CONFIG_TRACING) += trace_stat.o obj-$(CONFIG_TRACING) += trace_printk.o obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o diff --git a/lib/Makefile b/lib/Makefile index 7512dc978f18..a1aa1e81ed36 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -13,7 +13,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \ sha1.o md5.o irq_regs.o reciprocal_div.o argv_split.o \ proportions.o flex_proportions.o ratelimit.o show_mem.o \ is_single_threaded.o plist.o decompress.o kobject_uevent.o \ - earlycpio.o + earlycpio.o seq_buf.o obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o lib-$(CONFIG_MMU) += ioremap.o diff --git a/kernel/trace/seq_buf.c b/lib/seq_buf.c similarity index 100% rename from kernel/trace/seq_buf.c rename to lib/seq_buf.c -- GitLab