Re: [PATCH 2/2] staging: lustre: disable preempt while sampling processor id.
On Dec 18, 2017, at 16:01, NeilBrownwrote: > > Calling smp_processor_id() without disabling preemption > triggers a warning (if CONFIG_DEBUG_PREEMPT). > I think the result of cfs_cpt_current() is only used as a hint for > load balancing, rather than as a precise and stable indicator of > the current CPU. So it doesn't need to be called with > preemption disabled. > > So disable preemption inside cfs_cpt_current() to silence the warning. > > Signed-off-by: NeilBrown Reviewed-by: Andreas Dilger > --- > .../staging/lustre/lnet/libcfs/linux/linux-cpu.c | 13 +++-- > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c > b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c > index d30650f8dcb4..ca8518b8a3e0 100644 > --- a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c > +++ b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c > @@ -517,19 +517,20 @@ EXPORT_SYMBOL(cfs_cpt_spread_node); > int > cfs_cpt_current(struct cfs_cpt_table *cptab, int remap) > { > - int cpu = smp_processor_id(); > - int cpt = cptab->ctb_cpu2cpt[cpu]; > + int cpu; > + int cpt; > > - if (cpt < 0) { > - if (!remap) > - return cpt; > + preempt_disable(); > + cpu = smp_processor_id(); > + cpt = cptab->ctb_cpu2cpt[cpu]; > > + if (cpt < 0 && remap) { > /* don't return negative value for safety of upper layer, >* instead we shadow the unknown cpu to a valid partition ID >*/ > cpt = cpu % cptab->ctb_nparts; > } > - > + preempt_enable(); > return cpt; > } > EXPORT_SYMBOL(cfs_cpt_current); > > Cheers, Andreas -- Andreas Dilger Lustre Principal Architect Intel Corporation
Re: [PATCH 2/2] staging: lustre: disable preempt while sampling processor id.
On Dec 18, 2017, at 16:01, NeilBrown wrote: > > Calling smp_processor_id() without disabling preemption > triggers a warning (if CONFIG_DEBUG_PREEMPT). > I think the result of cfs_cpt_current() is only used as a hint for > load balancing, rather than as a precise and stable indicator of > the current CPU. So it doesn't need to be called with > preemption disabled. > > So disable preemption inside cfs_cpt_current() to silence the warning. > > Signed-off-by: NeilBrown Reviewed-by: Andreas Dilger > --- > .../staging/lustre/lnet/libcfs/linux/linux-cpu.c | 13 +++-- > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c > b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c > index d30650f8dcb4..ca8518b8a3e0 100644 > --- a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c > +++ b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c > @@ -517,19 +517,20 @@ EXPORT_SYMBOL(cfs_cpt_spread_node); > int > cfs_cpt_current(struct cfs_cpt_table *cptab, int remap) > { > - int cpu = smp_processor_id(); > - int cpt = cptab->ctb_cpu2cpt[cpu]; > + int cpu; > + int cpt; > > - if (cpt < 0) { > - if (!remap) > - return cpt; > + preempt_disable(); > + cpu = smp_processor_id(); > + cpt = cptab->ctb_cpu2cpt[cpu]; > > + if (cpt < 0 && remap) { > /* don't return negative value for safety of upper layer, >* instead we shadow the unknown cpu to a valid partition ID >*/ > cpt = cpu % cptab->ctb_nparts; > } > - > + preempt_enable(); > return cpt; > } > EXPORT_SYMBOL(cfs_cpt_current); > > Cheers, Andreas -- Andreas Dilger Lustre Principal Architect Intel Corporation
[PATCH 2/2] staging: lustre: disable preempt while sampling processor id.
Calling smp_processor_id() without disabling preemption triggers a warning (if CONFIG_DEBUG_PREEMPT). I think the result of cfs_cpt_current() is only used as a hint for load balancing, rather than as a precise and stable indicator of the current CPU. So it doesn't need to be called with preemption disabled. So disable preemption inside cfs_cpt_current() to silence the warning. Signed-off-by: NeilBrown--- .../staging/lustre/lnet/libcfs/linux/linux-cpu.c | 13 +++-- 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c index d30650f8dcb4..ca8518b8a3e0 100644 --- a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c +++ b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c @@ -517,19 +517,20 @@ EXPORT_SYMBOL(cfs_cpt_spread_node); int cfs_cpt_current(struct cfs_cpt_table *cptab, int remap) { - int cpu = smp_processor_id(); - int cpt = cptab->ctb_cpu2cpt[cpu]; + int cpu; + int cpt; - if (cpt < 0) { - if (!remap) - return cpt; + preempt_disable(); + cpu = smp_processor_id(); + cpt = cptab->ctb_cpu2cpt[cpu]; + if (cpt < 0 && remap) { /* don't return negative value for safety of upper layer, * instead we shadow the unknown cpu to a valid partition ID */ cpt = cpu % cptab->ctb_nparts; } - + preempt_enable(); return cpt; } EXPORT_SYMBOL(cfs_cpt_current);
[PATCH 2/2] staging: lustre: disable preempt while sampling processor id.
Calling smp_processor_id() without disabling preemption triggers a warning (if CONFIG_DEBUG_PREEMPT). I think the result of cfs_cpt_current() is only used as a hint for load balancing, rather than as a precise and stable indicator of the current CPU. So it doesn't need to be called with preemption disabled. So disable preemption inside cfs_cpt_current() to silence the warning. Signed-off-by: NeilBrown --- .../staging/lustre/lnet/libcfs/linux/linux-cpu.c | 13 +++-- 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c index d30650f8dcb4..ca8518b8a3e0 100644 --- a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c +++ b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c @@ -517,19 +517,20 @@ EXPORT_SYMBOL(cfs_cpt_spread_node); int cfs_cpt_current(struct cfs_cpt_table *cptab, int remap) { - int cpu = smp_processor_id(); - int cpt = cptab->ctb_cpu2cpt[cpu]; + int cpu; + int cpt; - if (cpt < 0) { - if (!remap) - return cpt; + preempt_disable(); + cpu = smp_processor_id(); + cpt = cptab->ctb_cpu2cpt[cpu]; + if (cpt < 0 && remap) { /* don't return negative value for safety of upper layer, * instead we shadow the unknown cpu to a valid partition ID */ cpt = cpu % cptab->ctb_nparts; } - + preempt_enable(); return cpt; } EXPORT_SYMBOL(cfs_cpt_current);