Messages in this thread | | | Subject | Re: [PATCH 1/2] perf: Fix failure to set cpumask when only one cpu | From | He Zhe <> | Date | Sat, 3 Aug 2019 13:34:11 +0800 |
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On 8/2/19 9:06 PM, Jiri Olsa wrote: > On Fri, Aug 02, 2019 at 04:29:51PM +0800, zhe.he@windriver.com wrote: >> From: He Zhe <zhe.he@windriver.com> >> >> The buffer containing string used to set cpumask is overwritten by end of >> string later in cpu_map__snprint_mask due to not enough memory space, when >> there is only one cpu. And thus causes the following failure. >> >> $ perf ftrace ls >> failed to reset ftrace >> >> This patch fixes the calculation of cpumask string size. >> >> Signed-off-by: He Zhe <zhe.he@windriver.com> >> --- >> tools/perf/builtin-ftrace.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c >> index 66d5a66..0193128 100644 >> --- a/tools/perf/builtin-ftrace.c >> +++ b/tools/perf/builtin-ftrace.c >> @@ -173,7 +173,7 @@ static int set_tracing_cpumask(struct cpu_map *cpumap) >> int last_cpu; >> >> last_cpu = cpu_map__cpu(cpumap, cpumap->nr - 1); >> - mask_size = (last_cpu + 3) / 4 + 1; >> + mask_size = last_cpu / 4 + 2; /* one more byte for EOS */ >> mask_size += last_cpu / 32; /* ',' is needed for every 32th cpus */ > ugh.. why do we care about last_cpu value in here at all? > > feels like using static buffer would be more reasonable
Thanks, and yes, a static buffer would be easy to handle. A 2KB buffer is enough to cover 8196 cpus, the maximum numbers of cpus we can run with for now.
Let's see if there is any other concerns.
Zhe
> > jirka > >> >> cpumask = malloc(mask_size); >> -- >> 2.7.4 >>
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