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Newer versions of glibc include a definition of struct sched_attr in
bits/sched.h (included through sched.h which is included by rtla).
Commit 0eecee340672 ("tools/rtla: fix collision with glibc
sched_attr/sched_set_attr") has modified the definition of struct
sched_attr in utils.h, so that it is only applied with older versions of
glibc that do not define it, in order to prevent build failure.
The definition in bits/sched.h depends on _GNU_SOURCE.
timerlat_bpf.c does not define _GNU_SOURCE, making it fall back to the
definition in utils.h. The latter has two fields less, leading to
shifted offsets of struct timerlat_params in timerlat_bpf_init.
Because of the shift, timerlat_bpf_init incorrectly reads
params->entries as 0 for timerlat-hist and disables the creation of
histogram maps, causing breakage in BPF sample collection mode:
$ rtla timerlat hist -d 1s
Error pulling BPF data
Fix the issue by also defining _GNU_SOURCE in timerlat_bpf.c.
Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Link: https://lore.kernel.org/20250430144651.621766-1-tglozar@redhat.com
Fixes: e34293ddcebd ("rtla/timerlat: Add BPF skeleton to collect samples")
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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Add BPF program that attaches to the osnoise:timerlat_sample tracepoint
and collects both the summary and the histogram (if requested) into BPF
maps (one map of each kind per context).
The program is designed to be used for both timerlat-top and
timerlat-hist. If using with timerlat-top, the "entries" parameter is
set to zero, which prevents the BPF program from recording histogram
entries. In that case, the maps for histograms do not have to be
created, as the BPF verifier will identify the code using them as
unreachable.
An IRQ or thread latency threshold might be supplied to stop recording
if hit, similar to the timerlat tracer threshold, which stops ftrace
tracing if hit. A BPF ringbuffer is used to signal threshold overflow to
userspace. In aa-only mode, this is the only function of the BPF
program.
Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Cc: Gabriele Monaco <gmonaco@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Link: https://lore.kernel.org/20250218145859.27762-5-tglozar@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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