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lib: dhry: fix unstable smp_processor_id(_) usage

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When running the in-kernel Dhrystone benchmark with
CONFIG_DEBUG_PREEMPT=y:

    BUG: using smp_processor_id() in preemptible [00000000] code: bash/938

Fix this by not using smp_processor_id() directly, but instead wrapping
the whole benchmark inside a get_cpu()/put_cpu() pair.  This makes sure
the whole benchmark is run on the same CPU core, and the reported values
are consistent.

Link: https://lkml.kernel.org/r/b0d29932bb24ad82cea7f821e295c898e9657be0.1678890070.git.geert+renesas@glider.be
Fixes: d5528cc168 ("lib: add Dhrystone benchmark test")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reported-by: Tobias Klausmann <klausman@schwarzvogel.de>
  Link: https://bugzilla.kernel.org/show_bug.cgi?id=217179
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Geert Uytterhoeven 2023-03-15 15:28:17 +01:00 committed by Andrew Morton
parent d2e44a50ec
commit 13684e966d
1 changed files with 4 additions and 2 deletions
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6
lib/dhry_run.c
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@ -31,6 +31,7 @@ MODULE_PARM_DESC(iterations,
static void dhry_benchmark(void)
{
unsigned int cpu = get_cpu();
int i, n;
if (iterations > 0) {
@ -45,9 +46,10 @@ static void dhry_benchmark(void)
}
report:
put_cpu();
if (n >= 0)
pr_info("CPU%u: Dhrystones per Second: %d (%d DMIPS)\n",
smp_processor_id(), n, n / DHRY_VAX);
pr_info("CPU%u: Dhrystones per Second: %d (%d DMIPS)\n", cpu,
n, n / DHRY_VAX);
else if (n == -EAGAIN)
pr_err("Please increase the number of iterations\n");
else