* [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message @ 2021-06-09 12:54 Zhen Lei 2021-06-11 10:32 ` Will Deacon 2021-06-15 19:18 ` Will Deacon 0 siblings, 2 replies; 10+ messages in thread From: Zhen Lei @ 2021-06-09 12:54 UTC (permalink / raw) To: Robin Murphy, linux-arm-kernel, Joerg Roedel, Will Deacon, iommu; +Cc: Zhen Lei Fixes scripts/checkpatch.pl warning: WARNING: Possible unnecessary 'out of memory' message Remove it can help us save a bit of memory. Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c index 2ddc3cd5a7d1..fd7c55b44881 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -2787,10 +2787,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu) void *strtab = smmu->strtab_cfg.strtab; cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); - if (!cfg->l1_desc) { - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n"); + if (!cfg->l1_desc) return -ENOMEM; - } for (i = 0; i < cfg->num_l1_ents; ++i) { arm_smmu_write_strtab_l1_desc(strtab, &cfg->l1_desc[i]); @@ -3581,10 +3579,8 @@ static int arm_smmu_device_probe(struct platform_device *pdev) bool bypass; smmu = devm_kzalloc(dev, sizeof(*smmu), GFP_KERNEL); - if (!smmu) { - dev_err(dev, "failed to allocate arm_smmu_device\n"); + if (!smmu) return -ENOMEM; - } smmu->dev = dev; if (dev->of_node) { -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message 2021-06-09 12:54 [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message Zhen Lei @ 2021-06-11 10:32 ` Will Deacon 2021-06-15 11:22 ` Leizhen (ThunderTown) 2021-06-15 19:18 ` Will Deacon 1 sibling, 1 reply; 10+ messages in thread From: Will Deacon @ 2021-06-11 10:32 UTC (permalink / raw) To: Zhen Lei; +Cc: Robin Murphy, linux-arm-kernel, Joerg Roedel, iommu On Wed, Jun 09, 2021 at 08:54:38PM +0800, Zhen Lei wrote: > Fixes scripts/checkpatch.pl warning: > WARNING: Possible unnecessary 'out of memory' message > > Remove it can help us save a bit of memory. > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > --- > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++------ > 1 file changed, 2 insertions(+), 6 deletions(-) > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > index 2ddc3cd5a7d1..fd7c55b44881 100644 > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > @@ -2787,10 +2787,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu) > void *strtab = smmu->strtab_cfg.strtab; > > cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); > - if (!cfg->l1_desc) { > - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n"); > + if (!cfg->l1_desc) What error do you get if devm_kzalloc() fails? I'd like to make sure it's easy to track down _which_ allocation failed in that case -- does it give you a line number, for example? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message 2021-06-11 10:32 ` Will Deacon @ 2021-06-15 11:22 ` Leizhen (ThunderTown) 2021-06-15 11:34 ` Will Deacon 0 siblings, 1 reply; 10+ messages in thread From: Leizhen (ThunderTown) @ 2021-06-15 11:22 UTC (permalink / raw) To: Will Deacon; +Cc: Robin Murphy, linux-arm-kernel, Joerg Roedel, iommu On 2021/6/11 18:32, Will Deacon wrote: > On Wed, Jun 09, 2021 at 08:54:38PM +0800, Zhen Lei wrote: >> Fixes scripts/checkpatch.pl warning: >> WARNING: Possible unnecessary 'out of memory' message >> >> Remove it can help us save a bit of memory. >> >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >> --- >> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++------ >> 1 file changed, 2 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >> index 2ddc3cd5a7d1..fd7c55b44881 100644 >> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >> @@ -2787,10 +2787,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu) >> void *strtab = smmu->strtab_cfg.strtab; >> >> cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); >> - if (!cfg->l1_desc) { >> - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n"); >> + if (!cfg->l1_desc) > > What error do you get if devm_kzalloc() fails? I'd like to make sure it's > easy to track down _which_ allocation failed in that case -- does it give > you a line number, for example? When devm_kzalloc() fails, the OOM information is printed. No line number information, but the size(order) and call stack is printed. It doesn't matter which allocation failed, the failure is caused by insufficient system memory rather than the fault of the SMMU driver. Therefore, the current printing is not helpful for locating the problem of insufficient memory. After all, when memory allocation fails, the SMMU driver cannot work at a lower specification. [ 44.126661] swapper/0 invoked oom-killer: gfp_mask=0x40cc0(GFP_KERNEL|__GFP_COMP), order=1, oom_score_adj=0 [ 44.136381] CPU: 26 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc6-00001-g0d973bf828c8 #1 [ 44.144436] Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V3.B220.02 03/27/2020 [ 44.153266] Call trace: [ 44.155703] dump_backtrace+0x0/0x1c0 [ 44.159355] show_stack+0x18/0x68 [ 44.162658] dump_stack+0xd8/0x134 [ 44.166047] dump_header+0x44/0x208 [ 44.169524] out_of_memory+0x530/0x580 [ 44.173256] __alloc_pages_slowpath.constprop.120+0x85c/0xac0 [ 44.178976] __alloc_pages+0x238/0x300 [ 44.182709] allocate_slab+0x3bc/0x3d8 [ 44.186440] ___slab_alloc+0x508/0x6b0 [ 44.190172] __slab_alloc.isra.100+0x2c/0x58 [ 44.194422] __kmalloc_node_track_caller+0x138/0x2e8 [ 44.199365] devm_kmalloc+0x58/0x100 [ 44.202926] arm_smmu_device_probe+0x858/0x1150 [ 44.207437] platform_probe+0x68/0xe0 > > Will > > . > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message 2021-06-15 11:22 ` Leizhen (ThunderTown) @ 2021-06-15 11:34 ` Will Deacon 2021-06-15 11:36 ` Will Deacon 2021-06-15 11:51 ` Robin Murphy 0 siblings, 2 replies; 10+ messages in thread From: Will Deacon @ 2021-06-15 11:34 UTC (permalink / raw) To: Leizhen (ThunderTown); +Cc: Robin Murphy, linux-arm-kernel, Joerg Roedel, iommu On Tue, Jun 15, 2021 at 07:22:10PM +0800, Leizhen (ThunderTown) wrote: > > > On 2021/6/11 18:32, Will Deacon wrote: > > On Wed, Jun 09, 2021 at 08:54:38PM +0800, Zhen Lei wrote: > >> Fixes scripts/checkpatch.pl warning: > >> WARNING: Possible unnecessary 'out of memory' message > >> > >> Remove it can help us save a bit of memory. > >> > >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > >> --- > >> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++------ > >> 1 file changed, 2 insertions(+), 6 deletions(-) > >> > >> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >> index 2ddc3cd5a7d1..fd7c55b44881 100644 > >> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >> @@ -2787,10 +2787,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu) > >> void *strtab = smmu->strtab_cfg.strtab; > >> > >> cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); > >> - if (!cfg->l1_desc) { > >> - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n"); > >> + if (!cfg->l1_desc) > > > > What error do you get if devm_kzalloc() fails? I'd like to make sure it's > > easy to track down _which_ allocation failed in that case -- does it give > > you a line number, for example? > > When devm_kzalloc() fails, the OOM information is printed. No line number information, but the > size(order) and call stack is printed. It doesn't matter which allocation failed, the failure > is caused by insufficient system memory rather than the fault of the SMMU driver. Therefore, > the current printing is not helpful for locating the problem of insufficient memory. After all, > when memory allocation fails, the SMMU driver cannot work at a lower specification. I don't entirely agree. Another reason for the failure is because the driver might be asking for a huge (or negative) allocation, in which case it might be instructive to have a look at the actual caller, particularly if the size is derived from hardware or firmware properties. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message 2021-06-15 11:34 ` Will Deacon @ 2021-06-15 11:36 ` Will Deacon 2021-06-15 11:51 ` Robin Murphy 1 sibling, 0 replies; 10+ messages in thread From: Will Deacon @ 2021-06-15 11:36 UTC (permalink / raw) To: Leizhen (ThunderTown); +Cc: Robin Murphy, linux-arm-kernel, Joerg Roedel, iommu On Tue, Jun 15, 2021 at 12:34:17PM +0100, Will Deacon wrote: > On Tue, Jun 15, 2021 at 07:22:10PM +0800, Leizhen (ThunderTown) wrote: > > > > > > On 2021/6/11 18:32, Will Deacon wrote: > > > On Wed, Jun 09, 2021 at 08:54:38PM +0800, Zhen Lei wrote: > > >> Fixes scripts/checkpatch.pl warning: > > >> WARNING: Possible unnecessary 'out of memory' message > > >> > > >> Remove it can help us save a bit of memory. > > >> > > >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > >> --- > > >> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++------ > > >> 1 file changed, 2 insertions(+), 6 deletions(-) > > >> > > >> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > >> index 2ddc3cd5a7d1..fd7c55b44881 100644 > > >> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > >> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > >> @@ -2787,10 +2787,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu) > > >> void *strtab = smmu->strtab_cfg.strtab; > > >> > > >> cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); > > >> - if (!cfg->l1_desc) { > > >> - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n"); > > >> + if (!cfg->l1_desc) > > > > > > What error do you get if devm_kzalloc() fails? I'd like to make sure it's > > > easy to track down _which_ allocation failed in that case -- does it give > > > you a line number, for example? > > > > When devm_kzalloc() fails, the OOM information is printed. No line number information, but the > > size(order) and call stack is printed. It doesn't matter which allocation failed, the failure > > is caused by insufficient system memory rather than the fault of the SMMU driver. Therefore, > > the current printing is not helpful for locating the problem of insufficient memory. After all, > > when memory allocation fails, the SMMU driver cannot work at a lower specification. > > I don't entirely agree. Another reason for the failure is because the driver > might be asking for a huge (or negative) allocation, in which case it might > be instructive to have a look at the actual caller, particularly if the > size is derived from hardware or firmware properties. That said, the callstack would solve this problem, so I think that's good enough. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message 2021-06-15 11:34 ` Will Deacon 2021-06-15 11:36 ` Will Deacon @ 2021-06-15 11:51 ` Robin Murphy 2021-06-15 11:55 ` Will Deacon 1 sibling, 1 reply; 10+ messages in thread From: Robin Murphy @ 2021-06-15 11:51 UTC (permalink / raw) To: Will Deacon, Leizhen (ThunderTown); +Cc: linux-arm-kernel, Joerg Roedel, iommu On 2021-06-15 12:34, Will Deacon wrote: > On Tue, Jun 15, 2021 at 07:22:10PM +0800, Leizhen (ThunderTown) wrote: >> >> >> On 2021/6/11 18:32, Will Deacon wrote: >>> On Wed, Jun 09, 2021 at 08:54:38PM +0800, Zhen Lei wrote: >>>> Fixes scripts/checkpatch.pl warning: >>>> WARNING: Possible unnecessary 'out of memory' message >>>> >>>> Remove it can help us save a bit of memory. >>>> >>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >>>> --- >>>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++------ >>>> 1 file changed, 2 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >>>> index 2ddc3cd5a7d1..fd7c55b44881 100644 >>>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >>>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >>>> @@ -2787,10 +2787,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu) >>>> void *strtab = smmu->strtab_cfg.strtab; >>>> >>>> cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); >>>> - if (!cfg->l1_desc) { >>>> - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n"); >>>> + if (!cfg->l1_desc) >>> >>> What error do you get if devm_kzalloc() fails? I'd like to make sure it's >>> easy to track down _which_ allocation failed in that case -- does it give >>> you a line number, for example? >> >> When devm_kzalloc() fails, the OOM information is printed. No line number information, but the >> size(order) and call stack is printed. It doesn't matter which allocation failed, the failure >> is caused by insufficient system memory rather than the fault of the SMMU driver. Therefore, >> the current printing is not helpful for locating the problem of insufficient memory. After all, >> when memory allocation fails, the SMMU driver cannot work at a lower specification. > > I don't entirely agree. Another reason for the failure is because the driver > might be asking for a huge (or negative) allocation, in which case it might > be instructive to have a look at the actual caller, particularly if the > size is derived from hardware or firmware properties. Agreed - other than deliberately-contrived situations I don't think I've ever hit a genuine OOM, but I definitely have debugged attempts to allocate -1 of something. If the driver-specific message actually calls out the critical information, e.g. "failed to allocate %d stream table entries", it gives debugging a head start since the miscalculation is obvious, but a static message that only identifies the callsite really only saves a quick trip to scripts/faddr2line, and personally I've never found that particularly valuable. Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message 2021-06-15 11:51 ` Robin Murphy @ 2021-06-15 11:55 ` Will Deacon 2021-06-16 1:47 ` Leizhen (ThunderTown) 0 siblings, 1 reply; 10+ messages in thread From: Will Deacon @ 2021-06-15 11:55 UTC (permalink / raw) To: Robin Murphy; +Cc: Leizhen (ThunderTown), linux-arm-kernel, Joerg Roedel, iommu On Tue, Jun 15, 2021 at 12:51:38PM +0100, Robin Murphy wrote: > On 2021-06-15 12:34, Will Deacon wrote: > > On Tue, Jun 15, 2021 at 07:22:10PM +0800, Leizhen (ThunderTown) wrote: > > > > > > > > > On 2021/6/11 18:32, Will Deacon wrote: > > > > On Wed, Jun 09, 2021 at 08:54:38PM +0800, Zhen Lei wrote: > > > > > Fixes scripts/checkpatch.pl warning: > > > > > WARNING: Possible unnecessary 'out of memory' message > > > > > > > > > > Remove it can help us save a bit of memory. > > > > > > > > > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > > > > --- > > > > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++------ > > > > > 1 file changed, 2 insertions(+), 6 deletions(-) > > > > > > > > > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > > > > index 2ddc3cd5a7d1..fd7c55b44881 100644 > > > > > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > > > > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > > > > @@ -2787,10 +2787,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu) > > > > > void *strtab = smmu->strtab_cfg.strtab; > > > > > cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); > > > > > - if (!cfg->l1_desc) { > > > > > - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n"); > > > > > + if (!cfg->l1_desc) > > > > > > > > What error do you get if devm_kzalloc() fails? I'd like to make sure it's > > > > easy to track down _which_ allocation failed in that case -- does it give > > > > you a line number, for example? > > > > > > When devm_kzalloc() fails, the OOM information is printed. No line number information, but the > > > size(order) and call stack is printed. It doesn't matter which allocation failed, the failure > > > is caused by insufficient system memory rather than the fault of the SMMU driver. Therefore, > > > the current printing is not helpful for locating the problem of insufficient memory. After all, > > > when memory allocation fails, the SMMU driver cannot work at a lower specification. > > > > I don't entirely agree. Another reason for the failure is because the driver > > might be asking for a huge (or negative) allocation, in which case it might > > be instructive to have a look at the actual caller, particularly if the > > size is derived from hardware or firmware properties. > > Agreed - other than deliberately-contrived situations I don't think I've > ever hit a genuine OOM, but I definitely have debugged attempts to allocate > -1 of something. If the driver-specific message actually calls out the > critical information, e.g. "failed to allocate %d stream table entries", it > gives debugging a head start since the miscalculation is obvious, but a > static message that only identifies the callsite really only saves a quick > trip to scripts/faddr2line, and personally I've never found that > particularly valuable. So it sounds like this particular patch is fine, but the one for smmuv2 should leave the IRQ allocation message alone (by virtue of it printing something a bit more useful -- the number of irqs). Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message 2021-06-15 11:55 ` Will Deacon @ 2021-06-16 1:47 ` Leizhen (ThunderTown) 2021-06-16 10:10 ` Will Deacon 0 siblings, 1 reply; 10+ messages in thread From: Leizhen (ThunderTown) @ 2021-06-16 1:47 UTC (permalink / raw) To: Will Deacon, Robin Murphy; +Cc: linux-arm-kernel, Joerg Roedel, iommu On 2021/6/15 19:55, Will Deacon wrote: > On Tue, Jun 15, 2021 at 12:51:38PM +0100, Robin Murphy wrote: >> On 2021-06-15 12:34, Will Deacon wrote: >>> On Tue, Jun 15, 2021 at 07:22:10PM +0800, Leizhen (ThunderTown) wrote: >>>> >>>> >>>> On 2021/6/11 18:32, Will Deacon wrote: >>>>> On Wed, Jun 09, 2021 at 08:54:38PM +0800, Zhen Lei wrote: >>>>>> Fixes scripts/checkpatch.pl warning: >>>>>> WARNING: Possible unnecessary 'out of memory' message >>>>>> >>>>>> Remove it can help us save a bit of memory. >>>>>> >>>>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >>>>>> --- >>>>>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++------ >>>>>> 1 file changed, 2 insertions(+), 6 deletions(-) >>>>>> >>>>>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >>>>>> index 2ddc3cd5a7d1..fd7c55b44881 100644 >>>>>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >>>>>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >>>>>> @@ -2787,10 +2787,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu) >>>>>> void *strtab = smmu->strtab_cfg.strtab; >>>>>> cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); >>>>>> - if (!cfg->l1_desc) { >>>>>> - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n"); >>>>>> + if (!cfg->l1_desc) >>>>> >>>>> What error do you get if devm_kzalloc() fails? I'd like to make sure it's >>>>> easy to track down _which_ allocation failed in that case -- does it give >>>>> you a line number, for example? >>>> >>>> When devm_kzalloc() fails, the OOM information is printed. No line number information, but the >>>> size(order) and call stack is printed. It doesn't matter which allocation failed, the failure >>>> is caused by insufficient system memory rather than the fault of the SMMU driver. Therefore, >>>> the current printing is not helpful for locating the problem of insufficient memory. After all, >>>> when memory allocation fails, the SMMU driver cannot work at a lower specification. >>> >>> I don't entirely agree. Another reason for the failure is because the driver >>> might be asking for a huge (or negative) allocation, in which case it might >>> be instructive to have a look at the actual caller, particularly if the >>> size is derived from hardware or firmware properties. >> >> Agreed - other than deliberately-contrived situations I don't think I've >> ever hit a genuine OOM, but I definitely have debugged attempts to allocate >> -1 of something. If the driver-specific message actually calls out the >> critical information, e.g. "failed to allocate %d stream table entries", it >> gives debugging a head start since the miscalculation is obvious, but a >> static message that only identifies the callsite really only saves a quick >> trip to scripts/faddr2line, and personally I've never found that >> particularly valuable. > > So it sounds like this particular patch is fine, but the one for smmuv2 > should leave the IRQ allocation message alone (by virtue of it printing > something a bit more useful -- the number of irqs). num_irqs = 0; while ((res = platform_get_resource(pdev, IORESOURCE_IRQ, num_irqs))) { num_irqs++; } As the above code, num_irqs is calculated based on the number of dtb or acpi configuration items, it can't be too large. That is, there is almost zero chance that devm_kcalloc() will fail because num_irqs is too large. > > Will > > . > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message 2021-06-16 1:47 ` Leizhen (ThunderTown) @ 2021-06-16 10:10 ` Will Deacon 0 siblings, 0 replies; 10+ messages in thread From: Will Deacon @ 2021-06-16 10:10 UTC (permalink / raw) To: Leizhen (ThunderTown); +Cc: Robin Murphy, linux-arm-kernel, Joerg Roedel, iommu On Wed, Jun 16, 2021 at 09:47:18AM +0800, Leizhen (ThunderTown) wrote: > > > On 2021/6/15 19:55, Will Deacon wrote: > > On Tue, Jun 15, 2021 at 12:51:38PM +0100, Robin Murphy wrote: > >> On 2021-06-15 12:34, Will Deacon wrote: > >>> On Tue, Jun 15, 2021 at 07:22:10PM +0800, Leizhen (ThunderTown) wrote: > >>>> > >>>> > >>>> On 2021/6/11 18:32, Will Deacon wrote: > >>>>> On Wed, Jun 09, 2021 at 08:54:38PM +0800, Zhen Lei wrote: > >>>>>> Fixes scripts/checkpatch.pl warning: > >>>>>> WARNING: Possible unnecessary 'out of memory' message > >>>>>> > >>>>>> Remove it can help us save a bit of memory. > >>>>>> > >>>>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > >>>>>> --- > >>>>>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++------ > >>>>>> 1 file changed, 2 insertions(+), 6 deletions(-) > >>>>>> > >>>>>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >>>>>> index 2ddc3cd5a7d1..fd7c55b44881 100644 > >>>>>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >>>>>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >>>>>> @@ -2787,10 +2787,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu) > >>>>>> void *strtab = smmu->strtab_cfg.strtab; > >>>>>> cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); > >>>>>> - if (!cfg->l1_desc) { > >>>>>> - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n"); > >>>>>> + if (!cfg->l1_desc) > >>>>> > >>>>> What error do you get if devm_kzalloc() fails? I'd like to make sure it's > >>>>> easy to track down _which_ allocation failed in that case -- does it give > >>>>> you a line number, for example? > >>>> > >>>> When devm_kzalloc() fails, the OOM information is printed. No line number information, but the > >>>> size(order) and call stack is printed. It doesn't matter which allocation failed, the failure > >>>> is caused by insufficient system memory rather than the fault of the SMMU driver. Therefore, > >>>> the current printing is not helpful for locating the problem of insufficient memory. After all, > >>>> when memory allocation fails, the SMMU driver cannot work at a lower specification. > >>> > >>> I don't entirely agree. Another reason for the failure is because the driver > >>> might be asking for a huge (or negative) allocation, in which case it might > >>> be instructive to have a look at the actual caller, particularly if the > >>> size is derived from hardware or firmware properties. > >> > >> Agreed - other than deliberately-contrived situations I don't think I've > >> ever hit a genuine OOM, but I definitely have debugged attempts to allocate > >> -1 of something. If the driver-specific message actually calls out the > >> critical information, e.g. "failed to allocate %d stream table entries", it > >> gives debugging a head start since the miscalculation is obvious, but a > >> static message that only identifies the callsite really only saves a quick > >> trip to scripts/faddr2line, and personally I've never found that > >> particularly valuable. > > > > So it sounds like this particular patch is fine, but the one for smmuv2 > > should leave the IRQ allocation message alone (by virtue of it printing > > something a bit more useful -- the number of irqs). > > num_irqs = 0; > while ((res = platform_get_resource(pdev, IORESOURCE_IRQ, num_irqs))) { > num_irqs++; > } > > As the above code, num_irqs is calculated based on the number of dtb or acpi > configuration items, it can't be too large. That is, there is almost zero chance > that devm_kcalloc() will fail because num_irqs is too large. Right, because firmware is never wrong about anything :) Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message 2021-06-09 12:54 [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message Zhen Lei 2021-06-11 10:32 ` Will Deacon @ 2021-06-15 19:18 ` Will Deacon 1 sibling, 0 replies; 10+ messages in thread From: Will Deacon @ 2021-06-15 19:18 UTC (permalink / raw) To: linux-arm-kernel, Zhen Lei, iommu, Joerg Roedel, Robin Murphy Cc: catalin.marinas, kernel-team, Will Deacon On Wed, 9 Jun 2021 20:54:38 +0800, Zhen Lei wrote: > Fixes scripts/checkpatch.pl warning: > WARNING: Possible unnecessary 'out of memory' message > > Remove it can help us save a bit of memory. Applied to will (for-joerg/arm-smmu/updates), thanks! [1/1] iommu/arm-smmu-v3: Remove unnecessary oom message https://git.kernel.org/will/c/affa909571b0 Cheers, -- Will https://fixes.arm64.dev https://next.arm64.dev https://will.arm64.dev _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2021-06-16 10:11 UTC | newest] Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-06-09 12:54 [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message Zhen Lei 2021-06-11 10:32 ` Will Deacon 2021-06-15 11:22 ` Leizhen (ThunderTown) 2021-06-15 11:34 ` Will Deacon 2021-06-15 11:36 ` Will Deacon 2021-06-15 11:51 ` Robin Murphy 2021-06-15 11:55 ` Will Deacon 2021-06-16 1:47 ` Leizhen (ThunderTown) 2021-06-16 10:10 ` Will Deacon 2021-06-15 19:18 ` Will Deacon
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).