kernel/linux.git/tools/lib/api/fs/tracing_path.c, branch v6.19.11

perf list: Give clues if failed to open tracing events directory

2024-08-01T15:11:33+00:00

When executing the command "perf list", I met "Error: failed to open tracing events directory" twice, the first reason is that there is no "/sys/kernel/tracing/events" directory due to it does not enable the kernel tracing infrastructure with CONFIG_FTRACE, the second reason is that there is no root privileges. Add the error string to tell the users what happened and what should to do, and also call put_tracing_file() to free events_path a little later to avoid messy code in the error message. At the same time, just remove the redundant "/" of the file path in the function get_tracing_file(), otherwise it shows something like "/sys/kernel/tracing//events". Before: $ ./perf list Error: failed to open tracing events directory After: (1) Without CONFIG_FTRACE $ ./perf list Error: failed to open tracing events directory /sys/kernel/tracing/events: No such file or directory (2) With CONFIG_FTRACE but no root privileges $ ./perf list Error: failed to open tracing events directory /sys/kernel/tracing/events: Permission denied Committer testing: Redirect stdout to null to quickly test the patch: Before: $ perf list > /dev/null Error: failed to open tracing events directory $ After: $ perf list > /dev/null Error: failed to open tracing events directory /sys/kernel/tracing/events: Permission denied $ Signed-off-by: Tiezhu Yang Tested-by: Arnaldo Carvalho de Melo Cc: Ingo Molnar Cc: Namhyung Kim Cc: Peter Zijlstra Link: https://lore.kernel.org/lkml/20240730062301.23244-3-yangtiezhu@loongson.cn Signed-off-by: Arnaldo Carvalho de Melo

tools lib api fs tracing_path: Remove two unused MAX_PATH paths

2023-05-28T13:23:00+00:00

tracing_mnt was set but never written. tracing_events_path was set and read on errors paths, but its value is exactly tracing_path with a "/events" appended, so we can derive the value in the error paths. There appears to have been a missing "/" when tracing_events_path was initialized. Signed-off-by: Ian Rogers Link: https://lore.kernel.org/r/20230526183401.2326121-8-irogers@google.com Cc: K Prateek Nayak Cc: Ravi Bangoria Cc: Mark Rutland Cc: Ross Zwisler Cc: Steven Rostedt (Google) Cc: Sean Christopherson Cc: Yang Jihong Cc: Peter Zijlstra Cc: Adrian Hunter Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Masami Hiramatsu (Google) Cc: Namhyung Kim Cc: Leo Yan Cc: Andi Kleen Cc: Alexander Shishkin Cc: Kan Liang Cc: Tiezhu Yang Cc: Ingo Molnar Cc: Paolo Bonzini Cc: linux-kernel@vger.kernel.org Cc: linux-perf-users@vger.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tracing: Always use canonical ftrace path

2023-02-18T19:34:09+00:00

The canonical location for the tracefs filesystem is at /sys/kernel/tracing. But, from Documentation/trace/ftrace.rst: Before 4.1, all ftrace tracing control files were within the debugfs file system, which is typically located at /sys/kernel/debug/tracing. For backward compatibility, when mounting the debugfs file system, the tracefs file system will be automatically mounted at: /sys/kernel/debug/tracing Many comments and Kconfig help messages in the tracing code still refer to this older debugfs path, so let's update them to avoid confusion. Link: https://lore.kernel.org/linux-trace-kernel/20230215223350.2658616-2-zwisler@google.com Acked-by: Masami Hiramatsu (Google) Reviewed-by: Mukesh Ojha Signed-off-by: Ross Zwisler Signed-off-by: Steven Rostedt (Google)

tools lib api fs tracing_path: Add scandir alphasort

2022-11-15T13:24:09+00:00

tracing_events__opendir() allows iteration over files in /tracing/events but with an arbitrary sort order. Add a scandir alternative where the results are alphabetically sorted. Signed-off-by: Ian Rogers Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Caleb Biggers Cc: Jiri Olsa Cc: Kajol Jain Cc: Kan Liang Cc: Leo Yan Cc: Mark Rutland Cc: Namhyung Kim Cc: Perry Taylor Cc: Peter Zijlstra Cc: Ravi Bangoria Cc: Rob Herring Cc: Sandipan Das Cc: Stephane Eranian Cc: Weilin Wang Cc: Xin Gao Cc: Xing Zhengjun Link: http://lore.kernel.org/lkml/20221114210723.2749751-4-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Fix tracing_path_mount proper path

2018-10-16T15:27:46+00:00

If there's no tracefs (RHEL7) support the tracing_path_mount returns debugfs path which results in following fail: # perf probe sys_write kprobe_events file does not exist - please rebuild kernel with CONFIG_KPROBE_EVENTS. Error: Failed to add events. In tracing_path_debugfs_mount function we need to return the 'tracing' path instead of just the mount to make it work: # perf probe sys_write Added new event: probe:sys_write (on sys_write) You can now use it in all perf tools, such as: perf record -e probe:sys_write -aR sleep 1 Adding the 'return tracing_path;' also to tracing_path_tracefs_mount function just for consistency with tracing_path_debugfs_mount. Upstream keeps working, because it has the tracefs support. Link: http://lkml.kernel.org/n/tip-yiwkzexq9fk1ey1xg3gnjlw4@git.kernel.org Signed-off-by: Jiri Olsa Cc: Alexander Shishkin Cc: Michael Petlan Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Steven Rostedt Fixes: 23773ca18b39 ("perf tools: Make perf aware of tracefs") Link: http://lkml.kernel.org/r/20181016114818.3595-1-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools lib api fs tracing_path: Make tracing_events_path private

2018-05-17T17:51:23+00:00

Not anymore accessed outside this library, keep it private. Cc: Adrian Hunter Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: https://lkml.kernel.org/n/tip-wg1m07flfrg1rm06jjzie8si@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools lib api fs tracing_path: Introduce opendir() method

2018-05-17T17:50:38+00:00

That takes care of using the right call to get the tracing_path directory, the one that will end up calling tracing_path_set() to figure out where tracefs is mounted. One more step in doing just lazy reading of system structures to reduce the number of operations done unconditionaly at 'perf' start. Cc: Adrian Hunter Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: https://lkml.kernel.org/n/tip-42zzi0f274909bg9mxzl81bu@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools lib api fs tracing_path: Introduce get/put_events_file() helpers

2018-05-17T15:01:50+00:00

To make reading events files a tad more compact than with get_tracing_files("events/foo"). Cc: Adrian Hunter Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: https://lkml.kernel.org/n/tip-do6xgtwpmfl8zjs1euxsd2du@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools lib api: Unexport 'tracing_path' variable

2018-05-16T19:27:14+00:00

One should use tracing_path_mount() instead, so more things get done lazily instead of at every 'perf' tool call startup. Cc: Adrian Hunter Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: https://lkml.kernel.org/n/tip-fci4yll35idd9yuslp67vqc2@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools lib api: The tracing_mnt variable doesn't need to be global

2018-05-16T19:20:12+00:00

Its only used in the file it is defined, so just make it static. Cc: Adrian Hunter Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: https://lkml.kernel.org/n/tip-p5x29u6mq2ml3mtnbg9844ad@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo