28.11.2015 14:13, Nikita Yushchenko пишет: >>> Not sure I understand logic behind this. With the current code, >>> resulting cpu_possible_mask depends on CONFIG_SMP_ON_UP: >>> - if it is set, cpu_possible_mask contains (0 1), as initialized in >>> arm_dt_init_cpu_maps() >>> - if it is not set, cpu_possible_mask contains (0), since >>> imx_smp_init_cpus() removes 1 from there. >> >> Right, adding debug to arch/arm/kernel/setup.c, just before the >> "if (is_smp())" shows: >> >> is_smp() 0 possible 3 present 1 online 1 >> >> which is totally wrong: if is_smp() is false, we should not be setting >> up any possible CPUs. See a patch below to fix that. >> >> However, this doesn't matter much, because the code in setup.c won't >> initialise the SMP operations struct ... > > But cpu start code is not the only place in the kernel that uses > cpu_present_mask. > > Are you sure that running with invalid cpu_present_mask has no side effects?
At least LTP suite does not like it: while running /opt/ltp/runtest/cpuhotplug, we see things like the above <<<test_start>>> tag=cpuhotplug02 stime=1446628761 cmdline="cpuhotplug02.sh -c 1 -l 1" contacts="" analysis=exit <<<test_output>>> Name: cpuhotplug02 Date: Wed Nov 4 09:19:21 UTC 2015 Desc: What happens to a process when its CPU is offlined? CPU is 1 /opt/ltp/testcases/bin/cpuhotplug_hotplug.sh: line 76: echo: write error: Function not implemented cpuhotplug02 1 TBROK : CPU1 cannot be onlined <<<execution_status>>> initiation_status="ok" duration=1 termination_type=exited termination_id=2 corefile=no cutime=4 cstime=6 <<<test_end>>> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
