tree ac2c0a93556e948ca1ffc2842128e35f7f367f69
parent 618c810a7b2163517ab1875bd56b633ca3cb3328
author Gabor Juhos <j4g8y7@gmail.com> 1751011134 +0200
committer Georgi Djakov <djakov@kernel.org> 1751049820 +0300

interconnect: avoid memory allocation when 'icc_bw_lock' is held

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 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: d30f83d278a9 ("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>