Re: [PATCH v1 1/6] perf header: Replace hardcoded max cpus by MAX_NR_CPUS

[Swapnil Sapkal]

Hello Arnaldo,

On 28-01-2026 23:45, Arnaldo Carvalho de Melo wrote:
> On Wed, Jan 28, 2026 at 09:55:05PM +0530, Swapnil Sapkal wrote:
> > Hi Srikanth, Arnaldo,
> >
> > Thank you for reviewing the patches.
> >
> > On 28-01-2026 13:09, Shrikanth Hegde wrote:
> > > On 1/28/26 12:19 AM, Swapnil Sapkal wrote:
> > > > cpumask and cpulist from cpu-domain header have hardcoded max_cpus value
> > > > of 1024. Current systems have more cpus than this value. Replace it with
> > > > MAX_NR_CPUS. Also define a macro to represent domain name length.
> > > >
> > > > Fixes: d40c68a49f69 ("perf header: Support CPU DOMAIN relation info")
> > > > Reported-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
> > > > Signed-off-by: Swapnil Sapkal <swapnil.sapkal@xxxxxxx>
> > > > ---
> > > >    tools/perf/util/header.c | 5 +++--
> > > >    1 file changed, 3 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> > > > index eefd1cd73b6a..31c3bab1b10a 100644
> > > > --- a/tools/perf/util/header.c
> > > > +++ b/tools/perf/util/header.c
> > > > @@ -76,6 +76,7 @@ static const u64 __perf_magic2    =
> > > > 0x32454c4946524550ULL;
> > > >    static const u64 __perf_magic2_sw = 0x50455246494c4532ULL;
> > > >    #define PERF_MAGIC    __perf_magic2
> > > > +#define DNAME_LEN    16
> > > >    const char perf_version_string[] = PERF_VERSION;
> > > > @@ -1616,10 +1617,10 @@ static int write_pmu_caps(struct feat_fd *ff,
> > > >    struct cpu_domain_map **build_cpu_domain_map(u32
> > > > *schedstat_version, u32 *max_sched_domains, u32 nr)
> > > >    {
> > > > +    char dname[DNAME_LEN], cpumask[MAX_NR_CPUS];
> > > >        struct domain_info *domain_info;
> > > >        struct cpu_domain_map **cd_map;
> > > > -    char dname[16], cpumask[256];
> > > > -    char cpulist[1024];
> > > > +    char cpulist[MAX_NR_CPUS];
> > > >        char *line = NULL;
> > > >        u32 cpu, domain;
> > > >        u32 dcount = 0;
> > >
> > > Looking at
> > > https://lore.kernel.org/all/20260119175833.340369-3-swapnil.sapkal@xxxxxxx/
> > >
> > > There was one more "char cpus[1024]"  in tools/perf/util/util.c.
> > > You may need to fix that too. It is unlikely but, if one has created
> > > exclusive
> > > cpusets comprising of only one cpu from a core, maybe you will run out
> > > the length.
> > > So better use the MAX_NR_CPUS there as well.
> >
> > Yes, I missed this.
> >
> > Arnaldo, can you please consider the below diff? Let me know if you'd like
> > me to respin the patch.
> >
> > --
> > Thanks and Regards,
> > Swapnil
> >
> > diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
> > index c83e59e8c787..3795d5182ce8 100644
> > --- a/tools/perf/util/util.c
> > +++ b/tools/perf/util/util.c
> > @@ -262,7 +262,7 @@ void cpumask_to_cpulist(char *cpumask, char *cpulist)
> >          int i, j, bm_size, nbits;
> >          int len = strlen(cpumask);
> >          unsigned long *bm;
> > -       char cpus[1024];
> > +       char cpus[MAX_NR_CPUS];
> >
> >          for (i = 0; i < len; i++) {
> >                  if (cpumask[i] == ',') {
> > diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
> > index 394dbfa944ac..c43f17137efd 100644
> > --- a/tools/perf/util/util.h
> > +++ b/tools/perf/util/util.h
> > @@ -6,6 +6,7 @@
> >   /* glibc 2.20 deprecates _BSD_SOURCE in favour of _DEFAULT_SOURCE */
> >   #define _DEFAULT_SOURCE 1
> >
> > +#include "perf.h"
>
> Why add it to util.h? I'll add it to where it is used, util.c, ok?

This doesn't need to be in util.h. Please move it to util.c

--
Thanks and Regards,
Swapnil

> - Arnaldo
>
> >   #include <dirent.h>
> >   #include <fcntl.h>
> >   #include <stdbool.h>