Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters | Date | Thu, 02 Apr 2020 01:29:14 +0200 |
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Peter Xu <peterx@redhat.com> writes:
> On Wed, Apr 01, 2020 at 10:30:08PM +0200, Thomas Gleixner wrote: >> Peter Xu <peterx@redhat.com> writes: >> > @@ -169,8 +169,12 @@ static int __init housekeeping_isolcpus_setup(char *str) >> > continue; >> > } >> > >> > - pr_warn("isolcpus: Error, unknown flag\n"); >> > - return 0; >> > + str = strchr(str, ','); >> > + if (str) >> > + /* Skip unknown sub-parameter */ >> > + str++; >> > + else >> > + return 0; >> >> Just looked at it again because I wanted to apply this and contrary to >> last time I figured out that this is broken: >> >> isolcpus=nohz,domain1,3,5 >> >> is a malformatted option, but the above will make it "valid" and result >> in: >> >> HK_FLAG_TICK and a cpumask of 3,5. > > I would think this is no worse than applying nothing - I read the > first "isalpha()" check as something like "the subparameter's first > character must not be a digit", so to differenciate with the cpu list. > If we keep this, we can still have subparams like "double-word".
It _is_ worse. If the intention is to write 'nohz,domain,1,3,5' and that missing comma morphs it silently into 'nohz,3,5' then this is really a step backwards. The upstream version would tell you that you screwed up.
>> static int __init housekeeping_isolcpus_setup(char *str) >> { >> unsigned int flags = 0; >> + char *par; >> + int len; >> >> while (isalpha(*str)) { >> if (!strncmp(str, "nohz,", 5)) { >> @@ -169,8 +171,17 @@ static int __init housekeeping_isolcpus_ >> 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; isalpha(*str); str++, len++); >> + if (*str != ',') { >> + pr_warn("isolcpus: Invalid flag %*s\n", len, par); > > ... this will dump "isolcpus: Invalid flag domain1,3,5", is this what > we wanted? Maybe only dumps "domain1"?
No, it will dump: "domain1" at least if my understanding of is_alpha() and the '%*s' format option is halfways correct
> For me so far I would still prefer the original one, giving more > freedom to the future params and the patch is also a bit easier (but I
Again. It does not matter whether the patch is easier or not. What matters is correctness and usability. Silently converting a typo into something else is horrible at best.
> definitely like the pr_warn when there's unknown subparams). But just > let me know your preference and I'll follow yours when repost.
Enforcing a pure 'is_alpha()' subparam space is not really a substantial restriction. Feel free to extend it by adding '|| *str == '_' if you really think that provides a value.
Thanks,
tglx
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