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Peter Wu 55c33dfbeb bpf: clarify when bpf_trace_printk discards lines
I opened /sys/kernel/tracing/trace once and kept reading from it.
bpf_trace_printk somehow did not seem to work, no entries were appended
to that trace file. It turns out that tracing is disabled when that file
is open. Save the next person some time and document this.

The trace file is described in Documentation/trace/ftrace.rst, however
the implication "tracing is disabled" did not immediate translate to
"bpf_trace_printk silently discards entries".

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-08-21 10:17:25 -07:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-08-06 18:44:57 -07:00
block
certs
crypto
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2019-08-13 16:24:57 -07:00
drivers net/mlx5e: Add AF_XDP need_wakeup support 2019-08-17 23:07:32 +02:00
fs Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-08-06 17:11:59 -07:00
include bpf: clarify when bpf_trace_printk discards lines 2019-08-21 10:17:25 -07:00
init
ipc
kernel bpf: clarify description for CONFIG_BPF_EVENTS 2019-08-21 10:17:24 -07:00
lib test_bpf: Fix a new clang warning about xor-ing two numbers 2019-08-20 17:07:29 +02:00
LICENSES
mm memremap: move from kernel/ to mm/ 2019-08-03 07:02:01 -07:00
net xdp: xdp_umem: replace kmap on vmap for umem map 2019-08-21 14:31:17 +02:00
samples samples: bpf: syscall_nrs: use mmap2 if defined 2019-08-21 14:31:38 +02:00
scripts btf: do not use CONFIG_OUTPUT_FORMAT 2019-08-21 14:57:17 +02:00
security
sound
tools libbpf: use LFS (_FILE_OFFSET_BITS) instead of direct mmap2 syscall 2019-08-21 14:31:17 +02:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-08-06 18:44:57 -07:00
Makefile Linux 5.3-rc3 2019-08-04 18:40:12 -07:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.