----- On Jan 10, 2017, at 8:01 AM, Thomas Gleixner [email protected] wrote:
> Mathieu reported that the LTTNG modules are broken as of 4.10-rc1 due to > the removal of the cpu hotplug notifiers. > > Usually I don't care much about out of tree modules, but LTTNG is widely > used in distros. There are two ways to solve that: > > 1) Reserve a hotplug state for LTTNG > > 2) Add a dynamic range for the prepare states. > > While #1 is the simplest solution, #2 is the proper one as we can convert > in tree users, which do not care about ordering, to the dynamic range as > well. > > Add a dynamic range which allows LTTNG to request states in the prepare > stage. I prepared a lttng-modules commit [1] that uses CPUHP_BP_PREPARE_DYN on 4.10 kernels, and it works fine through my cpu hotplug stress-testing. It's a very good cleanup! Thanks Thomas for this nice API. I'll be able to merge my commit into lttng-modules as soon as your patch lands into Linux mainline. Reviewed-by: Mathieu Desnoyers <[email protected]> Tested-by: Mathieu Desnoyers <[email protected]> Thanks, Mathieu [1] https://github.com/compudj/lttng-modules-dev/commit/f02214ac2e9a0f3d8d0270c0ac702c3143cdf120 > > Signed-off-by: Thomas Gleixner <[email protected]> > > --- > > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h > index 20bfefbe7594..d936a0021839 100644 > --- a/include/linux/cpuhotplug.h > +++ b/include/linux/cpuhotplug.h > @@ -74,6 +74,8 @@ enum cpuhp_state { > CPUHP_ZCOMP_PREPARE, > CPUHP_TIMERS_DEAD, > CPUHP_MIPS_SOC_PREPARE, > + CPUHP_BP_PREPARE_DYN, > + CPUHP_BP_PREPARE_DYN_END = CPUHP_BP_PREPARE_DYN + 20, > CPUHP_BRINGUP_CPU, > CPUHP_AP_IDLE_DEAD, > CPUHP_AP_OFFLINE, > diff --git a/kernel/cpu.c b/kernel/cpu.c > index f75c4d031eeb..c47506357519 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -1302,10 +1302,24 @@ static int cpuhp_cb_check(enum cpuhp_state state) > */ > static int cpuhp_reserve_state(enum cpuhp_state state) > { > - enum cpuhp_state i; > + enum cpuhp_state i, end; > + struct cpuhp_step *step; > > - for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) { > - if (!cpuhp_ap_states[i].name) > + switch (state) { > + case CPUHP_AP_ONLINE_DYN: > + step = cpuhp_ap_states + CPUHP_AP_ONLINE_DYN; > + end = CPUHP_AP_ONLINE_DYN_END; > + break; > + case CPUHP_BP_PREPARE_DYN: > + step = cpuhp_bp_states + CPUHP_BP_PREPARE_DYN; > + end = CPUHP_BP_PREPARE_DYN_END; > + break; > + default: > + return -EINVAL; > + } > + > + for (i = state; i <= end; i++, step++) { > + if (!step->name) > return i; > } > WARN(1, "No more dynamic states available for CPU hotplug\n"); > @@ -1323,7 +1337,7 @@ static int cpuhp_store_callbacks(enum cpuhp_state state, > const char *name, > > mutex_lock(&cpuhp_state_mutex); > > - if (state == CPUHP_AP_ONLINE_DYN) { > + if (state == CPUHP_AP_ONLINE_DYN || state == CPUHP_BP_PREPARE_DYN) { > ret = cpuhp_reserve_state(state); > if (ret < 0) > goto out; -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
