Commit c5b60592 authored Jun 27, 2025 by Gabor Juhos Committed by Georgi Djakov Jun 27, 2025

interconnect: avoid memory allocation when 'icc_bw_lock' is held



The 'icc_bw_lock' mutex is introduced in commit af42269c
("interconnect: Fix locking for runpm vs reclaim") in order to decouple
serialization of bw aggregation from codepaths that require memory
allocation.

However commit d30f83d2 ("interconnect: core: Add dynamic id
allocation support") added a devm_kasprintf() call into a path protected
by the 'icc_bw_lock' which causes the following lockdep warning on
machines like the Lenovo ThinkPad X13s:

    ======================================================
    WARNING: possible circular locking dependency detected
    6.16.0-rc3 #15 Not tainted
    ------------------------------------------------------
    (udev-worker)/342 is trying to acquire lock:
    ffffb973f7ec4638 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_node_track_caller_noprof+0xa0/0x3e0

    but task is already holding lock:
    ffffb973f7f7f0e8 (icc_bw_lock){+.+.}-{4:4}, at: icc_node_add+0x44/0x154

    which lock already depends on the new lock.

    the existing dependency chain (in reverse order) is:

    -> #1 (icc_bw_lock){+.+.}-{4:4}:
           icc_init+0x48/0x108
           do_one_initcall+0x64/0x30c
           kernel_init_freeable+0x27c/0x500
           kernel_init+0x20/0x1d8
           ret_from_fork+0x10/0x20

    -> #0 (fs_reclaim){+.+.}-{0:0}:
           __lock_acquire+0x136c/0x2114
           lock_acquire+0x1c8/0x354
           fs_reclaim_acquire+0x74/0xa8
           __kmalloc_node_track_caller_noprof+0xa0/0x3e0
           devm_kmalloc+0x54/0x124
           devm_kvasprintf+0x74/0xd4
           devm_kasprintf+0x58/0x80
           icc_node_add+0xb4/0x154
           qcom_osm_l3_probe+0x20c/0x314 [icc_osm_l3]
           platform_probe+0x68/0xd8
           really_probe+0xc0/0x38c
           __driver_probe_device+0x7c/0x160
           driver_probe_device+0x40/0x110
           __driver_attach+0xfc/0x208
           bus_for_each_dev+0x74/0xd0
           driver_attach+0x24/0x30
           bus_add_driver+0x110/0x234
           driver_register+0x60/0x128
           __platform_driver_register+0x24/0x30
           osm_l3_driver_init+0x20/0x1000 [icc_osm_l3]
           do_one_initcall+0x64/0x30c
           do_init_module+0x58/0x23c
           load_module+0x1df8/0x1f70
           init_module_from_file+0x88/0xc4
           idempotent_init_module+0x188/0x280
           __arm64_sys_finit_module+0x6c/0xd8
           invoke_syscall+0x48/0x110
           el0_svc_common.constprop.0+0xc0/0xe0
           do_el0_svc+0x1c/0x28
           el0_svc+0x4c/0x158
           el0t_64_sync_handler+0xc8/0xcc
           el0t_64_sync+0x198/0x19c

    other info that might help us debug this:

     Possible unsafe locking scenario:

           CPU0                    CPU1
           ----                    ----
      lock(icc_bw_lock);
                                   lock(fs_reclaim);
                                   lock(icc_bw_lock);
      lock(fs_reclaim);

     *** DEADLOCK ***

The icc_node_add() functions is not designed to fail, and as such it
should not do any memory allocation. In order to avoid this, add a new
helper function for the name generation to be called by drivers which
are using the new dynamic id feature.

Fixes: d30f83d2 ("interconnect: core: Add dynamic id allocation support")
Signed-off-by: Gabor Juhos <j4g8y7@gmail.com>
Link: https://lore.kernel.org/r/20250625-icc-bw-lockdep-v3-1-2b8f8b8987c4@gmail.com


Co-developed-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20250627075854.26943-1-johan+linaro@kernel.org


Signed-off-by: Georgi Djakov <djakov@kernel.org>

parent 618c810a

drivers/interconnect/core.c

+25 −4

Original line number	Diff line number	Diff line
		@@ -909,10 +909,35 @@ void icc_node_destroy(int id)
		return;

		kfree(node->links);
		if (node->id >= ICC_DYN_ID_START)
		kfree(node->name);
		kfree(node);
		}
		EXPORT_SYMBOL_GPL(icc_node_destroy);

		/**
		* icc_node_set_name() - set node name
		* @node: node
		* @provider: node provider
		* @name: node name
		*
		* Return: 0 on success, or -ENOMEM on allocation failure
		*/
		int icc_node_set_name(struct icc_node node, const struct icc_provider provider, const char *name)
		{
		if (node->id >= ICC_DYN_ID_START) {
		node->name = kasprintf(GFP_KERNEL, "%s@%s", name,
		dev_name(provider->dev));
		if (!node->name)
		return -ENOMEM;
		} else {
		node->name = name;
		}

		return 0;
		}
		EXPORT_SYMBOL_GPL(icc_node_set_name);

		/**
		* icc_link_nodes() - create link between two nodes
		* @src_node: source node
		@@ -1041,10 +1066,6 @@ void icc_node_add(struct icc_node node, struct icc_provider provider)
		node->avg_bw = node->init_avg;
		node->peak_bw = node->init_peak;

		if (node->id >= ICC_DYN_ID_START)
		node->name = devm_kasprintf(provider->dev, GFP_KERNEL, "%s@%s",
		node->name, dev_name(provider->dev));

		if (node->avg_bw \|\| node->peak_bw) {
		if (provider->pre_aggregate)
		provider->pre_aggregate(node);

drivers/interconnect/qcom/icc-rpmh.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -293,7 +293,12 @@ int qcom_icc_rpmh_probe(struct platform_device *pdev)
		goto err_remove_nodes;
		}

		node->name = qn->name;
		ret = icc_node_set_name(node, provider, qn->name);
		if (ret) {
		icc_node_destroy(node->id);
		goto err_remove_nodes;
		}

		node->data = qn;
		icc_node_add(node, provider);

drivers/interconnect/qcom/osm-l3.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -236,7 +236,12 @@ static int qcom_osm_l3_probe(struct platform_device *pdev)
		goto err;
		}

		node->name = qnodes[i]->name;
		ret = icc_node_set_name(node, provider, qnodes[i]->name);
		if (ret) {
		icc_node_destroy(node->id);
		goto err;
		}

		/* Cast away const and add it back in qcom_osm_l3_set() */
		node->data = (void *)qnodes[i];
		icc_node_add(node, provider);

include/linux/interconnect-provider.h

+7 −0

Original line number	Diff line number	Diff line
		@@ -119,6 +119,7 @@ int icc_std_aggregate(struct icc_node *node, u32 tag, u32 avg_bw,
		struct icc_node *icc_node_create_dyn(void);
		struct icc_node *icc_node_create(int id);
		void icc_node_destroy(int id);
		int icc_node_set_name(struct icc_node node, const struct icc_provider provider, const char *name);
		int icc_link_nodes(struct icc_node src_node, struct icc_node *dst_node);
		int icc_link_create(struct icc_node *node, const int dst_id);
		void icc_node_add(struct icc_node node, struct icc_provider provider);
		@@ -152,6 +153,12 @@ static inline void icc_node_destroy(int id)
		{
		}

		static inline int icc_node_set_name(struct icc_node node, const struct icc_provider provider,
		const char *name)
		{
		return -EOPNOTSUPP;
		}

		static inline int icc_link_nodes(struct icc_node src_node, struct icc_node *dst_node)
		{
		return -EOPNOTSUPP;