On 06/25/19 10:17, Nicholas Piggin wrote: > With the change to allow the boot CPU0 to be isolated, it is possible > to specify command line options that result in no housekeeping CPU > online at boot. > > An 8 CPU system booted with "nohz_full=0-6 maxcpus=4", for example. > > It is not easily possible at housekeeping init time to know all the > various SMP options that will result in an invalid configuration, so > this patch adds a sanity check after SMP init, to ensure that a > housekeeping CPU has been onlined. > > The panic is undesirable, but it's better than the alternative of an > obscure non deterministic failure. The panic will reliably happen > when advanced parameters are used incorrectly. > > Signed-off-by: Nicholas Piggin <npig...@gmail.com> > --- > v2: Fix a NULL pointer dereference when not overriding housekeeping, > noticed by kernel test robot and Qais, who fixed it and verified > the fix (thanks!)
Glad I could help. But for the record my problem wasn't a NULL pointer dereference and simply the loop didn't hit the condition to 'return 0' so I hit the panic. I tested that the fix does indeed skip the verification if no nohz_full nor isolcpus is passed. But I didn't do the reverse check, although from the code this flag is only set in housekeeping_setup() so it should continue to work as intended. Thanks! -- Qais Yousef
