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Tue, 15 Jun 2021 11:55:15 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 13D826145C; Tue, 15 Jun 2021 11:55:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1623758112; bh=/gr41PPAaRSOhX5e/haGfhwMpZ7WYsIfJ37HBrtlPqA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fwgBZ9enw2+xhYQfs4UdzXiJz5YYhnzJWKaVhGpaf9d9QCmClmJ1kGL9Jo1mQl/38 7UorMKcnnL9eWiIst0o5Veox1+gZ6CY5+MtMADKZbNfx998R66B+JujxfNKfVDGGGv KZsUQ5hJliuABc9o0m08ctAFyjWLC9i6p/+uuxAgMWBQV+0jjGy0DtOKnezZPuPmDa 5PQmhl+ypclZl5pHpwUc8J1s+NVYop3JooAZ85khqGPqUCTAbQBCmx/Noa9TrcoX/d hsmPq0/8qOdUoLKu3eu12EF/CVm5lIuCdboloEnXOio4V4XlC/edkLhJJY0kW5hPVm 2WVNUelHexkJQ== Date: Tue, 15 Jun 2021 12:55:08 +0100 From: Will Deacon To: Robin Murphy Cc: "Leizhen (ThunderTown)" , linux-arm-kernel , Joerg Roedel , iommu Subject: Re: [PATCH 1/1] iommu/arm-smmu-v3: remove unnecessary oom message Message-ID: <20210615115507.GD20598@willie-the-truck> References: <20210609125438.14369-1-thunder.leizhen@huawei.com> <20210611103220.GB15274@willie-the-truck> <2a0b7f37-156a-775f-ade4-015cade472c6@huawei.com> <20210615113417.GA20598@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210615_125514_167948_AB13790F X-CRM114-Status: GOOD ( 34.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 > > > > > --- > > > > > 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