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rtla/osnoise: Allow IPI filters to gracefully fail

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Kernels pre v6.6 won't have:

  39f7c41c90 ("tracing/filters: Enable filtering a cpumask field by another cpumask")

and thus won't be able to filter events using a user-provided cpumask, but
will still be capable of recording IPI events.

Make failing to set a filter for IPI events an acceptable error and fall
back to event handlers that do the filtering job themselves.

Suggested-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20260902123942.695822-5-vschneid@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
This commit is contained in:
Valentin Schneider 2026-09-02 14:39:33 +02:00 committed by Tomas Glozar
parent 9ca6a1662b
commit edbb1d2671
1 changed files with 46 additions and 5 deletions
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51
tools/tracing/rtla/src/osnoise_top.c
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@ -314,6 +314,30 @@ osnoise_ipi_cpu_handler(struct trace_seq *s, struct tep_record *record,
return 0;
}
/*
* osnoise_ipi_cpu_unfiltered_handler - this is the handler for single CPU IPI
* events. Slightly less optimized than
* the filtered variant.
*/
static int
osnoise_ipi_cpu_unfiltered_handler(struct trace_seq *s, struct tep_record *record,
struct tep_event *event, void *context)
{
struct osnoise_tool *tool;
unsigned long long dst_cpu;
struct osnoise_params *params;
struct trace_instance *trace = context;
tool = container_of(trace, struct osnoise_tool, trace);
params = to_osnoise_params(tool->params);
tep_get_field_val(s, event, "cpu", record, &dst_cpu, 1);
if (CPU_ISSET(dst_cpu, &params->common.monitored_cpus))
account_ipi(tool, dst_cpu);
return 0;
}
static cpu_set_t cpumask_tmp_cpus;
/*
@ -344,7 +368,7 @@ osnoise_ipi_cpumask_handler(struct trace_seq *s, struct tep_record *record,
}
/*
* Despite already filtering for such an intersection, we need to compute
* Even if already filtering for such an intersection, we need to compute
* the intersection here as the @cpumask field may contain non-monitored
* CPUs.
*/
@ -369,6 +393,7 @@ osnoise_ipi_cpumask_handler(struct trace_seq *s, struct tep_record *record,
*/
struct osnoise_tool *osnoise_init_top(struct common_params *params)
{
bool ipi_filters_enabled = false;
struct osnoise_tool *tool;
int retval;
@ -403,6 +428,8 @@ struct osnoise_tool *osnoise_init_top(struct common_params *params)
/*
* If tracing on a subset of possible CPUs, leverage the kernel filtering
* infrastructure to only generate events on traced CPUs.
* Older kernels (pre v6.6) may have the IPI events but not the ability
* to filter them, so allow that to fail gracefully.
*/
if (params->cpus) {
char filter[MAX_PATH];
@ -412,8 +439,8 @@ struct osnoise_tool *osnoise_init_top(struct common_params *params)
"ipi", "ipi_send_cpu", "filter",
filter);
if (retval < 0) {
err_msg("Could not set ipi_send_cpu CPU filter\n");
goto out_err;
debug_msg("Could not set ipi_send_cpu CPU filter\n");
goto no_filter;
}
@ -422,13 +449,27 @@ struct osnoise_tool *osnoise_init_top(struct common_params *params)
"ipi", "ipi_send_cpumask", "filter",
filter);
if (retval < 0) {
/*
* If we managed to set up the previous filter but not
* this one, something's really wrong
*/
err_msg("Could not set ipi_send_cpumask CPU filter\n");
goto out_err;
}
}
ipi_filters_enabled = true;
}
no_filter:
/*
* If no filtering is available and we're tracing all CPUs, we can still
* use the filtered callback since stats are collected for all CPUs.
*/
tep_register_event_handler(tool->trace.tep, -1, "ipi", "ipi_send_cpu",
osnoise_ipi_cpu_handler, NULL);
(!params->cpus || ipi_filters_enabled) ?
osnoise_ipi_cpu_handler :
osnoise_ipi_cpu_unfiltered_handler,
NULL);
tep_register_event_handler(tool->trace.tep, -1, "ipi", "ipi_send_cpumask",
osnoise_ipi_cpumask_handler, NULL);