6.12-stable review patch. If anyone has any objections, please let me know.
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From: Tomas Glozar tglozar@redhat.com
[ Upstream commit 4eba4723c5254ba8251ecb7094a5078d5c300646 ]
Most fields of struct timerlat_top_cpu are unsigned long long, but the fields {irq,thread,user}_count are int (32-bit signed).
This leads to overflow when tracing on a large number of CPUs for a long enough time: $ rtla timerlat top -a20 -c 1-127 -d 12h ... 0 12:00:00 | IRQ Timer Latency (us) | Thread Timer Latency (us) CPU COUNT | cur min avg max | cur min avg max 1 #43200096 | 0 0 1 2 | 3 2 6 12 ... 127 #43200096 | 0 0 1 2 | 3 2 5 11 ALL #119144 e4 | 0 5 4 | 2 28 16
The average latency should be 0-1 for IRQ and 5-6 for thread, but is reported as 5 and 28, about 4 to 5 times more, due to the count overflowing when summed over all CPUs: 43200096 * 127 = 5486412192, however, 1191444898 (= 5486412192 mod MAX_INT) is reported instead, as seen on the last line of the output, and the averages are thus ~4.6 times higher than they should be (5486412192 / 1191444898 = ~4.6).
Fix the issue by changing {irq,thread,user}_count fields to unsigned long long, similarly to other fields in struct timerlat_top_cpu and to the count variable in timerlat_top_print_sum.
Link: https://lore.kernel.org/20241011121015.2868751-1-tglozar@redhat.com Reported-by: Attila Fazekas afazekas@redhat.com Signed-off-by: Tomas Glozar tglozar@redhat.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- tools/tracing/rtla/src/timerlat_top.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c index 3b62519a412fc..ac2ff38a57ee5 100644 --- a/tools/tracing/rtla/src/timerlat_top.c +++ b/tools/tracing/rtla/src/timerlat_top.c @@ -54,9 +54,9 @@ struct timerlat_top_params { };
struct timerlat_top_cpu { - int irq_count; - int thread_count; - int user_count; + unsigned long long irq_count; + unsigned long long thread_count; + unsigned long long user_count;
unsigned long long cur_irq; unsigned long long min_irq; @@ -280,7 +280,7 @@ static void timerlat_top_print(struct osnoise_tool *top, int cpu) /* * Unless trace is being lost, IRQ counter is always the max. */ - trace_seq_printf(s, "%3d #%-9d |", cpu, cpu_data->irq_count); + trace_seq_printf(s, "%3d #%-9llu |", cpu, cpu_data->irq_count);
if (!cpu_data->irq_count) { trace_seq_printf(s, "%s %s %s %s |", no_value, no_value, no_value, no_value);