From: Peter Xu peterx@redhat.com
[ Upstream commit 3662daf023500dc084fa3b96f68a6f46179ddc73 ]
The "isolcpus=" parameter allows sub-parameters before the cpulist is specified, and if the parser detects an unknown sub-parameters the whole parameter will be ignored.
This design is incompatible with itself when new sub-parameters are added. An older kernel will not recognize the new sub-parameter and will invalidate the whole parameter so the CPU isolation will not take effect. It emits a warning:
isolcpus: Error, unknown flag
The better and compatible way is to allow "isolcpus=" to skip unknown sub-parameters, so that even if new sub-parameters are added an older kernel will still be able to behave as usual even if with the new sub-parameter specified on the command line.
Ideally this should have been there when the first sub-parameter for "isolcpus=" was introduced.
Suggested-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Peter Xu peterx@redhat.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Link: https://lkml.kernel.org/r/20200403223517.406353-1-peterx@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 008d6ac2342b7..808244f3ddd98 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 */