Messages in this thread | | | Date | Tue, 14 Apr 2020 17:57:15 -0400 | From | Peter Xu <> | Subject | Re: [PATCH v3] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters |
| |
Ping - Thomas, do you think this version is ok to you?
This has missed 5.7 already, am I right?
Thanks,
On Fri, Apr 03, 2020 at 06:35:17PM -0400, Peter Xu wrote: > The "isolcpus=" parameter allows sub-parameters to exist before the > cpulist is specified, and if it sees unknown sub-parameters the whole > parameter will be ignored. This design is incompatible with itself > when we add more sub-parameters to "isolcpus=", because the old > kernels will not recognize the new "isolcpus=" sub-parameters, then it > will invalidate the whole parameter so the CPU isolation will not > really take effect if we start to use the new sub-parameters while > later we reboot into an old kernel. Instead we will see this when > booting the old kernel: > > isolcpus: Error, unknown flag > > The better and compatible way is to allow "isolcpus=" to skip unknown > sub-parameters, so that even if we add new sub-parameters to it the > old kernel will still be able to behave as usual even if with the new > sub-parameter is specified. > > Ideally this patch should be there when we introduce the first > sub-parameter for "isolcpus=", so it's already a bit late. However > late is better than nothing. > > CC: Ming Lei <ming.lei@redhat.com> > CC: Ingo Molnar <mingo@redhat.com> > CC: Peter Zijlstra <peterz@infradead.org> > CC: Juri Lelli <juri.lelli@redhat.com> > CC: Luiz Capitulino <lcapitulino@redhat.com> > Suggested-by: Thomas Gleixner <tglx@linutronix.de> > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > v3: > - add brackets for for loop > - move "illegal" a bit higher, which may look tiny bit nicer > - also allow '_' > v2: > - only allow isalpha() for sub-parameters [tglx] > --- > kernel/sched/isolation.c | 21 +++++++++++++++++++-- > 1 file changed, 19 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c > index 008d6ac2342b..808244f3ddd9 100644 > --- a/kernel/sched/isolation.c > +++ b/kernel/sched/isolation.c > @@ -149,6 +149,9 @@ __setup("nohz_full=", housekeeping_nohz_full_setup); > static int __init housekeeping_isolcpus_setup(char *str) > { > unsigned int flags = 0; > + bool illegal = false; > + char *par; > + int len; > > while (isalpha(*str)) { > if (!strncmp(str, "nohz,", 5)) { > @@ -169,8 +172,22 @@ static int __init housekeeping_isolcpus_setup(char *str) > continue; > } > > - pr_warn("isolcpus: Error, unknown flag\n"); > - return 0; > + /* > + * Skip unknown sub-parameter and validate that it is not > + * containing an invalid character. > + */ > + for (par = str, len = 0; *str && *str != ','; str++, len++) { > + if (!isalpha(*str) && *str != '_') > + illegal = true; > + } > + > + if (illegal) { > + pr_warn("isolcpus: Invalid flag %.*s\n", len, par); > + return 0; > + } > + > + pr_info("isolcpus: Skipped unknown flag %.*s\n", len, par); > + str++; > } > > /* Default behaviour for isolcpus without flags */ > -- > 2.24.1 >
-- Peter Xu
| |