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[93.89.165.28]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4535eac8c41sm5947235e9.26.2025.06.18.12.38.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Jun 2025 12:38:25 -0700 (PDT) Message-ID: <5f8c1163-d347-4c93-968c-3fd191336f04@gmail.com> Date: Wed, 18 Jun 2025 21:38:23 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] interconnect: avoid memory allocation when 'icc_bw_lock' is held Content-Language: hu To: Johan Hovold , Georgi Djakov Cc: Raviteja Laggyshetty , Bryan O'Donoghue , linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250529-icc-bw-lockdep-v1-1-3d714b6a9374@gmail.com> From: Gabor Juhos In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Johan, Thank you for taking a look into this. 2025. 06. 18. 14:43 keltezéssel, Johan Hovold írta: > On Thu, May 29, 2025 at 04:46:22PM +0200, Gabor Juhos wrote: >> The 'icc_bw_lock' mutex is introduced in commit af42269c3523 >> ("interconnect: Fix locking for runpm vs reclaim") in order >> to decouple serialization of bw aggregation from codepaths >> that require memory allocation. >> >> However commit d30f83d278a9 ("interconnect: core: Add dynamic >> id allocation support") added a devm_kasprintf() call into a >> path protected by the 'icc_bw_lock' which causes this lockdep >> warning (at least on the IPQ9574 platform): >> >> ====================================================== >> WARNING: possible circular locking dependency detected >> 6.15.0-next-20250529 #0 Not tainted >> ------------------------------------------------------ >> swapper/0/1 is trying to acquire lock: >> ffffffc081df57d8 (icc_bw_lock){+.+.}-{4:4}, at: icc_init+0x8/0x108 >> >> but task is already holding lock: >> ffffffc081d7db10 (fs_reclaim){+.+.}-{0:0}, at: icc_init+0x28/0x108 >> >> which lock already depends on the new lock. > > Thanks for fixing this. I get a similar splat with sc8280xp and the > icc_ism_l3 driver since 6.16-rc1. > > Georgi, this is a regression that prevents lockdep from being used on a > bunch of Qualcomm platforms and should be fixed in mainline ASAP (e.g. > to avoid further locking issues from being introduced). > >> Move the memory allocation part of the code outside of the protected >> path to eliminate the warning. Also add a note about why it is moved >> to there, >> >> Fixes: d30f83d278a9 ("interconnect: core: Add dynamic id allocation support") >> Signed-off-by: Gabor Juhos >> --- >> drivers/interconnect/core.c | 14 ++++++++++---- >> 1 file changed, 10 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c >> index 1a41e59c77f85a811f78986e98401625f4cadfa3..acdb3b8f1e54942dbb1b71ec2b170b08ad709e6b 100644 >> --- a/drivers/interconnect/core.c >> +++ b/drivers/interconnect/core.c >> @@ -1023,6 +1023,16 @@ void icc_node_add(struct icc_node *node, struct icc_provider *provider) >> return; >> >> mutex_lock(&icc_lock); >> + >> + if (node->id >= ICC_DYN_ID_START) { >> + /* >> + * Memory allocation must be done outside of codepaths >> + * protected by icc_bw_lock. >> + */ >> + node->name = devm_kasprintf(provider->dev, GFP_KERNEL, "%s@%s", >> + node->name, dev_name(provider->dev)); >> + } > > The node name has already been set by the caller and the node has not > been added yet, so I think you should move this before taking the > icc_lock. It seems reasonable. I will send a modified version, which also contains handling of memory allocation failures. > >> + >> mutex_lock(&icc_bw_lock); >> >> node->provider = provider; > > With that addressed, feel free to add my: > > Reviewed-by: Johan Hovold > Tested-by: Johan Hovold Regards, Gabor