Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
tracing: Use atomic_inc_return() for updating "disabled" counter in irqsoff tracer
The irqsoff tracer uses the per CPU "disabled" field to prevent corruption
of the accounting when it starts to trace interrupts disabled, but there's
a slight race that could happen if for some reason it was called twice.
Use atomic_inc_return() instead.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/20250505212236.567884756@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
+18
-11
+18
-11
kernel/trace/trace_irqsoff.c
+18
-11
kernel/trace/trace_irqsoff.c
···
397
397
int cpu;
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struct trace_array *tr = irqsoff_trace;
399
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struct trace_array_cpu *data;
400
+
long disabled;
400
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if (!tracer_enabled || !tracing_is_enabled())
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return;
···
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if (unlikely(!data) || local_read(&data->disabled))
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return;
414
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-
local_inc(&data->disabled);
414
+
disabled = local_inc_return(&data->disabled);
416
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417
-
data->critical_sequence = max_sequence;
418
-
data->preempt_timestamp = ftrace_now(cpu);
419
-
data->critical_start = parent_ip ? : ip;
416
+
if (disabled == 1) {
417
+
data->critical_sequence = max_sequence;
418
+
data->preempt_timestamp = ftrace_now(cpu);
419
+
data->critical_start = parent_ip ? : ip;
420
420
421
-
__trace_function(tr, ip, parent_ip, tracing_gen_ctx());
421
+
__trace_function(tr, ip, parent_ip, tracing_gen_ctx());
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423
-
per_cpu(tracing_cpu, cpu) = 1;
423
+
per_cpu(tracing_cpu, cpu) = 1;
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+
}
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local_dec(&data->disabled);
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}
···
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struct trace_array *tr = irqsoff_trace;
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struct trace_array_cpu *data;
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unsigned int trace_ctx;
434
+
long disabled;
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cpu = raw_smp_processor_id();
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/* Always clear the tracing cpu on stopping the trace */
···
452
448
!data->critical_start || local_read(&data->disabled))
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return;
454
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455
-
local_inc(&data->disabled);
451
+
disabled = local_inc_return(&data->disabled);
456
452
457
-
trace_ctx = tracing_gen_ctx();
458
-
__trace_function(tr, ip, parent_ip, trace_ctx);
459
-
check_critical_timing(tr, data, parent_ip ? : ip, cpu);
460
-
data->critical_start = 0;
453
+
if (disabled == 1) {
454
+
trace_ctx = tracing_gen_ctx();
455
+
__trace_function(tr, ip, parent_ip, trace_ctx);
456
+
check_critical_timing(tr, data, parent_ip ? : ip, cpu);
457
+
data->critical_start = 0;
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+
}
459
+
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local_dec(&data->disabled);
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461
}
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462