When called from xive_irq_startup(), the size of the cpumask can be
larger than nr_cpu_ids. Most of time, its value is NR_CPUS (2048).
This can result in such WARNINGs in xive_find_target_in_mask():
[ 0.094480] WARNING: CPU: 10 PID: 1 at ../arch/powerpc/sysdev/xive/common.c:476 xive_find_target_in_mask+0x110/0x2f0
[ 0.094486] Modules linked in:
[ 0.094491] CPU: 10 PID: 1 Comm: swapper/0 Not tainted 4.12.0+ #3
[ 0.094496] task: c0000003fae4f200 task.stack: c0000003fe108000
[ 0.094501] NIP: c00000000008a310 LR: c00000000008a2e4 CTR: 000000000072ca34
[ 0.094506] REGS: c0000003fe10b360 TRAP: 0700 Not tainted (4.12.0+)
[ 0.094510] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE>
[ 0.094515] CR: 88000222 XER: 20040008
[ 0.094521] CFAR: c00000000008a2cc SOFTE: 0
[ 0.094521] GPR00: c00000000008a274 c0000003fe10b5e0 c000000001428f00 0000000000000010
[ 0.094521] GPR04: 0000000000000010 0000000000000010 0000000000000010 0000000000000099
[ 0.094521] GPR08: 0000000000000010 0000000000000001 ffffffffffff0000 0000000000000000
[ 0.094521] GPR12: 0000000000000000 c00000000fff2d00 c00000000000d4d8 0000000000000000
[ 0.094521] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 0.094521] GPR20: 0000000000000000 0000000000000000 0000000000000000 c000000000b451e8
[ 0.094521] GPR24: 00000000ffffffff c000000001462354 0000000000000800 00000000000007ff
[ 0.094521] GPR28: c000000001462354 0000000000000010 c0000003f857e418 0000000000000010
[ 0.094580] NIP [c00000000008a310] xive_find_target_in_mask+0x110/0x2f0
[ 0.094585] LR [c00000000008a2e4] xive_find_target_in_mask+0xe4/0x2f0
[ 0.094589] Call Trace:
[ 0.094593] [c0000003fe10b5e0] [c00000000008a274] xive_find_target_in_mask+0x74/0x2f0 (unreliable)
[ 0.094601] [c0000003fe10b690] [c00000000008abf0] xive_pick_irq_target.isra.1+0x200/0x230
[ 0.094608] [c0000003fe10b830] [c00000000008b250] xive_irq_startup+0x60/0x180
[ 0.094614] [c0000003fe10b8b0] [c0000000001608f0] irq_startup+0x70/0xd0
[ 0.094620] [c0000003fe10b8f0] [c00000000015df7c] __setup_irq+0x7bc/0x880
[ 0.094626] [c0000003fe10ba90] [c00000000015e30c] request_threaded_irq+0x14c/0x2c0
[ 0.094632] [c0000003fe10baf0] [c0000000000aeb00] request_event_sources_irqs+0x100/0x180
[ 0.094639] [c0000003fe10bc10] [c000000000e7d2f8] __machine_initcall_pseries_init_ras_IRQ+0x104/0x134
[ 0.094646] [c0000003fe10bc40] [c00000000000cc88] do_one_initcall+0x68/0x1d0
[ 0.094652] [c0000003fe10bd00] [c000000000e643c8] kernel_init_freeable+0x290/0x374
[ 0.094658] [c0000003fe10bdc0] [c00000000000d4f4] kernel_init+0x24/0x170
[ 0.094664] [c0000003fe10be30] [c00000000000b268] ret_from_kernel_thread+0x5c/0x74
[ 0.094669] Instruction dump:
[ 0.094673] 48586529 60000000 e8dc0002 393f0001 7f9b4800 7c7d07b4 7d3f07b4 409effcc
[ 0.094682] 7f9d3000 7d26e850 79290fe0 69290001 <0b090000> 409c0194 3f620004 3b7b8ec8
Fix this problem by using a minimum value.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
arch/powerpc/sysdev/xive/common.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
index 536ee15f61fb..4dac7d560a42 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c
@@ -463,7 +463,7 @@ static int xive_find_target_in_mask(const struct cpumask *mask,
int cpu, first, num, i;
/* Pick up a starting point CPU in the mask based on fuzz */
- num = cpumask_weight(mask);
+ num = min_t(int, cpumask_weight(mask), nr_cpu_ids);
first = fuzz % num;
/* Locate it */
--
2.7.5
C=C3=A9dric Le Goater [off-list ref] writes:
When called from xive_irq_startup(), the size of the cpumask can be
larger than nr_cpu_ids. Most of time, its value is NR_CPUS (2048).
Ugh, you're right.
#define nr_cpumask_bits ((unsigned int)NR_CPUS)
...
/**
* cpumask_weight - Count of bits in *srcp
* @srcp: the cpumask to count bits (< nr_cpu_ids) in.
*/
static inline unsigned int cpumask_weight(const struct cpumask *srcp)
{
return bitmap_weight(cpumask_bits(srcp), nr_cpumask_bits);
}
I don't know what the comment on srcp is trying to say. It's not true
that it only counts nr_cpu_ids worth of bits.
So it does seem if we're passed a mask with > nr_cpu_ids bits set then
cpumask_weight() will return > nr_cpu_ids, which is .. unhelpful.
BUT, I don't see other code handling cpumask_weight() returning >
nr_cpu_ids - at least I can't find any with some grepping.
So what is going wrong here that we're being passed a mask with more
than nr_cpu_ids bits set?
I think the affinity mask is copied to the desc in desc_smp_init(), and
the call chain will be:
irq_create_mapping()
-> irq_domain_alloc_descs()
-> __irq_alloc_descs()
-> alloc_descs()
-> alloc_desc()
-> desc_set_defaults()
-> desc_smp_init()
irq_create_mapping() is doing:
virq =3D irq_domain_alloc_descs(-1, 1, hwirq, of_node_to_nid(of_node), NU=
LL);
Where the affinity mask is the NULL at the end.
So presumably we're hitting the irq_default_affinity case here:
static void desc_smp_init(struct irq_desc *desc, int node,
const struct cpumask *affinity)
{
if (!affinity)
affinity =3D irq_default_affinity;
cpumask_copy(desc->irq_common_data.affinity, affinity);
Which comes from:
static void __init init_irq_default_affinity(void)
{
#ifdef CONFIG_CPUMASK_OFFSTACK
if (!irq_default_affinity)
zalloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
#endif
if (cpumask_empty(irq_default_affinity))
cpumask_setall(irq_default_affinity);
}
And cpumask_setall() will indeed set NR_CPUs bits.
So that all seems sane, except that it does mean cpumask_weight() can
return > nr_cpu_ids which is awkward.
I guess this patch is a good fix, I'll expand the change log a bit.
cheers
This can result in such WARNINGs in xive_find_target_in_mask():
[ 0.094480] WARNING: CPU: 10 PID: 1 at ../arch/powerpc/sysdev/xive/=
common.c:476 xive_find_target_in_mask+0x110/0x2f0
[ 0.094486] Modules linked in:
[ 0.094491] CPU: 10 PID: 1 Comm: swapper/0 Not tainted 4.12.0+ #3
[ 0.094496] task: c0000003fae4f200 task.stack: c0000003fe108000
[ 0.094501] NIP: c00000000008a310 LR: c00000000008a2e4 CTR: 0000000=
00072ca34
[ 0.094506] REGS: c0000003fe10b360 TRAP: 0700 Not tainted (4.12.=
0+)
[ 0.094510] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE>
[ 0.094515] CR: 88000222 XER: 20040008
[ 0.094521] CFAR: c00000000008a2cc SOFTE: 0
[ 0.094521] GPR00: c00000000008a274 c0000003fe10b5e0 c000000001428f=
00 0000000000000010
[ 0.094521] GPR04: 0000000000000010 0000000000000010 00000000000000=
10 0000000000000099
[ 0.094521] GPR08: 0000000000000010 0000000000000001 ffffffffffff00=
00 0000000000000000
[ 0.094521] GPR12: 0000000000000000 c00000000fff2d00 c00000000000d4=
d8 0000000000000000
[ 0.094521] GPR16: 0000000000000000 0000000000000000 00000000000000=
00 0000000000000000
[ 0.094521] GPR20: 0000000000000000 0000000000000000 00000000000000=
00 c000000000b451e8
[ 0.094521] GPR24: 00000000ffffffff c000000001462354 00000000000008=
00 00000000000007ff
[ 0.094521] GPR28: c000000001462354 0000000000000010 c0000003f857e4=
18 0000000000000010
[ 0.094580] NIP [c00000000008a310] xive_find_target_in_mask+0x110/0=
x2f0
[ 0.094585] LR [c00000000008a2e4] xive_find_target_in_mask+0xe4/0x2=
f0
[ 0.094589] Call Trace:
[ 0.094593] [c0000003fe10b5e0] [c00000000008a274] xive_find_target_=
in_mask+0x74/0x2f0 (unreliable)
[ 0.094601] [c0000003fe10b690] [c00000000008abf0] xive_pick_irq_tar=
get.isra.1+0x200/0x230
[ 0.094608] [c0000003fe10b830] [c00000000008b250] xive_irq_startup+=
0x60/0x180
[ 0.094614] [c0000003fe10b8b0] [c0000000001608f0] irq_startup+0x70/=
0xd0
[ 0.094620] [c0000003fe10b8f0] [c00000000015df7c] __setup_irq+0x7bc=
/0x880
[ 0.094626] [c0000003fe10ba90] [c00000000015e30c] request_threaded_=
irq+0x14c/0x2c0
[ 0.094632] [c0000003fe10baf0] [c0000000000aeb00] request_event_sou=
rces_irqs+0x100/0x180
[ 0.094639] [c0000003fe10bc10] [c000000000e7d2f8] __machine_initcal=
l_pseries_init_ras_IRQ+0x104/0x134
[ 0.094646] [c0000003fe10bc40] [c00000000000cc88] do_one_initcall+0=
x68/0x1d0
[ 0.094652] [c0000003fe10bd00] [c000000000e643c8] kernel_init_freea=
ble+0x290/0x374
[ 0.094658] [c0000003fe10bdc0] [c00000000000d4f4] kernel_init+0x24/=
0x170
[ 0.094664] [c0000003fe10be30] [c00000000000b268] ret_from_kernel_t=
hread+0x5c/0x74
[ 0.094669] Instruction dump:
[ 0.094673] 48586529 60000000 e8dc0002 393f0001 7f9b4800 7c7d07b4 7=
d3f07b4 409effcc
[ 0.094682] 7f9d3000 7d26e850 79290fe0 69290001 <0b090000> 409c0194=
3f620004 3b7b8ec8
quoted hunk
Fix this problem by using a minimum value.
Signed-off-by: C=C3=A9dric Le Goater <clg@kaod.org>
---
arch/powerpc/sysdev/xive/common.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive=
/common.c
quoted hunk
index 536ee15f61fb..4dac7d560a42 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c
@@ -463,7 +463,7 @@ static int xive_find_target_in_mask(const struct cpum=
ask *mask,
int cpu, first, num, i;
=20=20
/* Pick up a starting point CPU in the mask based on fuzz */
- num =3D cpumask_weight(mask);
+ num =3D min_t(int, cpumask_weight(mask), nr_cpu_ids);
first =3D fuzz % num;
=20=20
/* Locate it */
--=20
2.7.5
On Wed, 2017-08-09 at 17:06 +1000, Michael Ellerman wrote:
/**
* cpumask_weight - Count of bits in *srcp
* @srcp: the cpumask to count bits (< nr_cpu_ids) in.
*/
static inline unsigned int cpumask_weight(const struct cpumask *srcp)
{
return bitmap_weight(cpumask_bits(srcp), nr_cpumask_bits);
}
I don't know what the comment on srcp is trying to say. It's not true
that it only counts nr_cpu_ids worth of bits.
Right, and that's what bit me. We should report that on lkml and maybe
propose a patch that crops the result...
Cheers,
Ben.
On 08/09/2017 09:06 AM, Michael Ellerman wrote:
Cédric Le Goater [off-list ref] writes:
quoted
When called from xive_irq_startup(), the size of the cpumask can be
larger than nr_cpu_ids. Most of time, its value is NR_CPUS (2048).
Ugh, you're right.
#define nr_cpumask_bits ((unsigned int)NR_CPUS)
...
/**
* cpumask_weight - Count of bits in *srcp
* @srcp: the cpumask to count bits (< nr_cpu_ids) in.
*/
static inline unsigned int cpumask_weight(const struct cpumask *srcp)
{
return bitmap_weight(cpumask_bits(srcp), nr_cpumask_bits);
}
I don't know what the comment on srcp is trying to say. It's not true
that it only counts nr_cpu_ids worth of bits.
So it does seem if we're passed a mask with > nr_cpu_ids bits set then
cpumask_weight() will return > nr_cpu_ids, which is .. unhelpful.
BUT, I don't see other code handling cpumask_weight() returning >
nr_cpu_ids - at least I can't find any with some grepping.
So what is going wrong here that we're being passed a mask with more
than nr_cpu_ids bits set?
I think the affinity mask is copied to the desc in desc_smp_init(), and
the call chain will be:
irq_create_mapping()
-> irq_domain_alloc_descs()
-> __irq_alloc_descs()
-> alloc_descs()
-> alloc_desc()
-> desc_set_defaults()
-> desc_smp_init()
irq_create_mapping() is doing:
virq = irq_domain_alloc_descs(-1, 1, hwirq, of_node_to_nid(of_node), NULL);
Where the affinity mask is the NULL at the end.
So presumably we're hitting the irq_default_affinity case here:
static void desc_smp_init(struct irq_desc *desc, int node,
const struct cpumask *affinity)
{
if (!affinity)
affinity = irq_default_affinity;
cpumask_copy(desc->irq_common_data.affinity, affinity);
Which comes from:
static void __init init_irq_default_affinity(void)
{
#ifdef CONFIG_CPUMASK_OFFSTACK
if (!irq_default_affinity)
zalloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
#endif
if (cpumask_empty(irq_default_affinity))
cpumask_setall(irq_default_affinity);
}
And cpumask_setall() will indeed set NR_CPUs bits.
So that all seems sane, except that it does mean cpumask_weight() can
return > nr_cpu_ids which is awkward.
I guess this patch is a good fix, I'll expand the change log a bit.
Yes. Thanks for the digging. I didn't do as much.
Cheers,
C.