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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 01/11] xen: sched: make implementing .alloc_pdata optional
On 06/04/16 18:22, Dario Faggioli wrote:
> The .alloc_pdata scheduler hook must, before this change,
> be implemented by all schedulers --even those ones that
> don't need to allocate anything.
>
> Make it possible to just use the SCHED_OP(), like for
> the other hooks, by using ERR_PTR() and IS_ERR() for
> error reporting. This:
> - makes NULL a variant of success;
> - allows for errors other than ENOMEM to be properly
> communicated (if ever necessary).
>
> This, in turn, means that schedulers not needing to
> allocate any per-pCPU data, can avoid implementing the
> hook. In fact, the artificial implementation of
> .alloc_pdata in the ARINC653 is removed (and, while there,
> nuke .free_pdata too, as it is equally useless).
>
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> Reviewed-by: Meng Xu <mengxu@xxxxxxxxxxxxx>
Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>
> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> Cc: Robert VanVossen <robert.vanvossen@xxxxxxxxxxxxxxx>
> Cc: Josh Whitehead <josh.whitehead@xxxxxxxxxxxxxxx>
> Cc: Jan Beulich <JBeulich@xxxxxxxx>
> Cc: Juergen Gross <jgross@xxxxxxxx>
> ---
> Changes from v1:
> * only update sd->sched_priv if alloc_pdata does not return
> IS_ERR, so that xfree() can always be safely called on
> sd->sched_priv itself, as requested during review;
> * xen/err.h included in .c files that actually need it,
> instead than in sched-if.h.
> ---
> xen/common/sched_arinc653.c | 31 -------------------------------
> xen/common/sched_credit.c | 5 +++--
> xen/common/sched_credit2.c | 2 +-
> xen/common/sched_rt.c | 8 ++++----
> xen/common/schedule.c | 27 +++++++++++++++++----------
> 5 files changed, 25 insertions(+), 48 deletions(-)
>
> diff --git a/xen/common/sched_arinc653.c b/xen/common/sched_arinc653.c
> index 8a11a2f..b79fcdf 100644
> --- a/xen/common/sched_arinc653.c
> +++ b/xen/common/sched_arinc653.c
> @@ -456,34 +456,6 @@ a653sched_free_vdata(const struct scheduler *ops, void
> *priv)
> }
>
> /**
> - * This function allocates scheduler-specific data for a physical CPU
> - *
> - * We do not actually make use of any per-CPU data but the hypervisor expects
> - * a non-NULL return value
> - *
> - * @param ops Pointer to this instance of the scheduler structure
> - *
> - * @return Pointer to the allocated data
> - */
> -static void *
> -a653sched_alloc_pdata(const struct scheduler *ops, int cpu)
> -{
> - /* return a non-NULL value to keep schedule.c happy */
> - return SCHED_PRIV(ops);
> -}
> -
> -/**
> - * This function frees scheduler-specific data for a physical CPU
> - *
> - * @param ops Pointer to this instance of the scheduler structure
> - */
> -static void
> -a653sched_free_pdata(const struct scheduler *ops, void *pcpu, int cpu)
> -{
> - /* nop */
> -}
> -
> -/**
> * This function allocates scheduler-specific data for a domain
> *
> * We do not actually make use of any per-domain data but the hypervisor
> @@ -737,9 +709,6 @@ static const struct scheduler sched_arinc653_def = {
> .free_vdata = a653sched_free_vdata,
> .alloc_vdata = a653sched_alloc_vdata,
>
> - .free_pdata = a653sched_free_pdata,
> - .alloc_pdata = a653sched_alloc_pdata,
> -
> .free_domdata = a653sched_free_domdata,
> .alloc_domdata = a653sched_alloc_domdata,
>
> diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
> index 4c4927f..63a4a63 100644
> --- a/xen/common/sched_credit.c
> +++ b/xen/common/sched_credit.c
> @@ -23,6 +23,7 @@
> #include <xen/errno.h>
> #include <xen/keyhandler.h>
> #include <xen/trace.h>
> +#include <xen/err.h>
>
>
> /*
> @@ -532,12 +533,12 @@ csched_alloc_pdata(const struct scheduler *ops, int cpu)
> /* Allocate per-PCPU info */
> spc = xzalloc(struct csched_pcpu);
> if ( spc == NULL )
> - return NULL;
> + return ERR_PTR(-ENOMEM);
>
> if ( !alloc_cpumask_var(&spc->balance_mask) )
> {
> xfree(spc);
> - return NULL;
> + return ERR_PTR(-ENOMEM);
> }
>
> spin_lock_irqsave(&prv->lock, flags);
> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
> index b8c8e40..e97d8be 100644
> --- a/xen/common/sched_credit2.c
> +++ b/xen/common/sched_credit2.c
> @@ -2047,7 +2047,7 @@ csched2_alloc_pdata(const struct scheduler *ops, int
> cpu)
> printk("%s: cpu %d not online yet, deferring initializatgion\n",
> __func__, cpu);
>
> - return (void *)1;
> + return NULL;
> }
>
> static void
> diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
> index 321b0a5..aece318 100644
> --- a/xen/common/sched_rt.c
> +++ b/xen/common/sched_rt.c
> @@ -29,6 +29,7 @@
> #include <xen/cpu.h>
> #include <xen/keyhandler.h>
> #include <xen/trace.h>
> +#include <xen/err.h>
> #include <xen/guest_access.h>
>
> /*
> @@ -681,7 +682,7 @@ rt_alloc_pdata(const struct scheduler *ops, int cpu)
> spin_unlock_irqrestore(old_lock, flags);
>
> if ( !alloc_cpumask_var(&_cpumask_scratch[cpu]) )
> - return NULL;
> + return ERR_PTR(-ENOMEM);
>
> if ( prv->repl_timer == NULL )
> {
> @@ -689,13 +690,12 @@ rt_alloc_pdata(const struct scheduler *ops, int cpu)
> prv->repl_timer = xzalloc(struct timer);
>
> if ( prv->repl_timer == NULL )
> - return NULL;
> + return ERR_PTR(-ENOMEM);
>
> init_timer(prv->repl_timer, repl_timer_handler, (void *)ops, cpu);
> }
>
> - /* 1 indicates alloc. succeed in schedule.c */
> - return (void *)1;
> + return NULL;
> }
>
> static void
> diff --git a/xen/common/schedule.c b/xen/common/schedule.c
> index b7dee16..1941613 100644
> --- a/xen/common/schedule.c
> +++ b/xen/common/schedule.c
> @@ -37,6 +37,7 @@
> #include <xen/event.h>
> #include <public/sched.h>
> #include <xsm/xsm.h>
> +#include <xen/err.h>
>
> /* opt_sched: scheduler - default to configured value */
> static char __initdata opt_sched[10] = CONFIG_SCHED_DEFAULT;
> @@ -1462,6 +1463,7 @@ static void poll_timer_fn(void *data)
> static int cpu_schedule_up(unsigned int cpu)
> {
> struct schedule_data *sd = &per_cpu(schedule_data, cpu);
> + void *sched_priv;
>
> per_cpu(scheduler, cpu) = &ops;
> spin_lock_init(&sd->_lock);
> @@ -1500,9 +1502,16 @@ static int cpu_schedule_up(unsigned int cpu)
> if ( idle_vcpu[cpu] == NULL )
> return -ENOMEM;
>
> - if ( (ops.alloc_pdata != NULL) &&
> - ((sd->sched_priv = ops.alloc_pdata(&ops, cpu)) == NULL) )
> - return -ENOMEM;
> + /*
> + * We don't want to risk calling xfree() on an sd->sched_priv
> + * (e.g., inside free_pdata, from cpu_schedule_down() called
> + * during CPU_UP_CANCELLED) that contains an IS_ERR value.
> + */
> + sched_priv = SCHED_OP(&ops, alloc_pdata, cpu);
> + if ( IS_ERR(sched_priv) )
> + return PTR_ERR(sched_priv);
> +
> + sd->sched_priv = sched_priv;
>
> return 0;
> }
> @@ -1512,8 +1521,7 @@ static void cpu_schedule_down(unsigned int cpu)
> struct schedule_data *sd = &per_cpu(schedule_data, cpu);
> struct scheduler *sched = per_cpu(scheduler, cpu);
>
> - if ( sd->sched_priv != NULL )
> - SCHED_OP(sched, free_pdata, sd->sched_priv, cpu);
> + SCHED_OP(sched, free_pdata, sd->sched_priv, cpu);
> SCHED_OP(sched, free_vdata, idle_vcpu[cpu]->sched_priv);
>
> idle_vcpu[cpu]->sched_priv = NULL;
> @@ -1608,9 +1616,8 @@ void __init scheduler_init(void)
> idle_domain->max_vcpus = nr_cpu_ids;
> if ( alloc_vcpu(idle_domain, 0, 0) == NULL )
> BUG();
> - if ( ops.alloc_pdata &&
> - !(this_cpu(schedule_data).sched_priv = ops.alloc_pdata(&ops, 0)) )
> - BUG();
> + this_cpu(schedule_data).sched_priv = SCHED_OP(&ops, alloc_pdata, 0);
> + BUG_ON(IS_ERR(this_cpu(schedule_data).sched_priv));
> SCHED_OP(&ops, init_pdata, this_cpu(schedule_data).sched_priv, 0);
> }
>
> @@ -1653,8 +1660,8 @@ int schedule_cpu_switch(unsigned int cpu, struct
> cpupool *c)
>
> idle = idle_vcpu[cpu];
> ppriv = SCHED_OP(new_ops, alloc_pdata, cpu);
> - if ( ppriv == NULL )
> - return -ENOMEM;
> + if ( IS_ERR(ppriv) )
> + return PTR_ERR(ppriv);
> SCHED_OP(new_ops, init_pdata, ppriv, cpu);
> vpriv = SCHED_OP(new_ops, alloc_vdata, idle, idle->domain->sched_priv);
> if ( vpriv == NULL )
>
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