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tracing: Use atomic_inc_return() for updating "disabled" counter in irqsoff tracer

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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>
This commit is contained in:
Steven Rostedt 2025-05-05 17:21:16 -04:00 committed by Steven Rostedt (Google)
parent 90633c34c3
commit c4a80c0615
1 changed files with 18 additions and 11 deletions
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29
kernel/trace/trace_irqsoff.c
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@ -397,6 +397,7 @@ start_critical_timing(unsigned long ip, unsigned long parent_ip)
int cpu;
struct trace_array *tr = irqsoff_trace;
struct trace_array_cpu *data;
long disabled;
if (!tracer_enabled || !tracing_is_enabled())
return;
@ -411,15 +412,17 @@ start_critical_timing(unsigned long ip, unsigned long parent_ip)
if (unlikely(!data) || local_read(&data->disabled))
return;
local_inc(&data->disabled);
disabled = local_inc_return(&data->disabled);
data->critical_sequence = max_sequence;
data->preempt_timestamp = ftrace_now(cpu);
data->critical_start = parent_ip ? : ip;
if (disabled == 1) {
data->critical_sequence = max_sequence;
data->preempt_timestamp = ftrace_now(cpu);
data->critical_start = parent_ip ? : ip;
__trace_function(tr, ip, parent_ip, tracing_gen_ctx());
__trace_function(tr, ip, parent_ip, tracing_gen_ctx());
per_cpu(tracing_cpu, cpu) = 1;
per_cpu(tracing_cpu, cpu) = 1;
}
local_dec(&data->disabled);
}
@ -431,6 +434,7 @@ stop_critical_timing(unsigned long ip, unsigned long parent_ip)
struct trace_array *tr = irqsoff_trace;
struct trace_array_cpu *data;
unsigned int trace_ctx;
long disabled;
cpu = raw_smp_processor_id();
/* Always clear the tracing cpu on stopping the trace */
@ -448,12 +452,15 @@ stop_critical_timing(unsigned long ip, unsigned long parent_ip)
!data->critical_start || local_read(&data->disabled))
return;
local_inc(&data->disabled);
disabled = local_inc_return(&data->disabled);
if (disabled == 1) {
trace_ctx = tracing_gen_ctx();
__trace_function(tr, ip, parent_ip, trace_ctx);
check_critical_timing(tr, data, parent_ip ? : ip, cpu);
data->critical_start = 0;
}
trace_ctx = tracing_gen_ctx();
__trace_function(tr, ip, parent_ip, trace_ctx);
check_critical_timing(tr, data, parent_ip ? : ip, cpu);
data->critical_start = 0;
local_dec(&data->disabled);
}