[ Upstream commit 6f63af7511e7058f3fa4ad5b8102210741c9f947 ]
We don't need to hold the prepare_lock when dropping a ref on a struct
clk_core. The release function is only freeing memory and any code with
a pointer reference has already unlinked anything pointing to the
clk_core. This reduces the holding area of the prepare_lock a bit.
Note that we also don't call free_clk() with the prepare_lock held.
There isn't any reason to do that.
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20240325184204.745706-3-sboyd@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit e581cf5d216289ef292d1a4036d53ce90e122469 ]
Doug reported [1] the following hung task:
INFO: task swapper/0:1 blocked for more than 122 seconds.
Not tainted 5.15.149-21875-gf795ebc40eb8 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:swapper/0 state:D stack: 0 pid: 1 ppid: 0 flags:0x00000008
Call trace:
__switch_to+0xf4/0x1f4
__schedule+0x418/0xb80
schedule+0x5c/0x10c
rpm_resume+0xe0/0x52c
rpm_resume+0x178/0x52c
__pm_runtime_resume+0x58/0x98
clk_pm_runtime_get+0x30/0xb0
clk_disable_unused_subtree+0x58/0x208
clk_disable_unused_subtree+0x38/0x208
clk_disable_unused_subtree+0x38/0x208
clk_disable_unused_subtree+0x38/0x208
clk_disable_unused_subtree+0x38/0x208
clk_disable_unused+0x4c/0xe4
do_one_initcall+0xcc/0x2d8
do_initcall_level+0xa4/0x148
do_initcalls+0x5c/0x9c
do_basic_setup+0x24/0x30
kernel_init_freeable+0xec/0x164
kernel_init+0x28/0x120
ret_from_fork+0x10/0x20
INFO: task kworker/u16:0:9 blocked for more than 122 seconds.
Not tainted 5.15.149-21875-gf795ebc40eb8 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u16:0 state:D stack: 0 pid: 9 ppid: 2 flags:0x00000008
Workqueue: events_unbound deferred_probe_work_func
Call trace:
__switch_to+0xf4/0x1f4
__schedule+0x418/0xb80
schedule+0x5c/0x10c
schedule_preempt_disabled+0x2c/0x48
__mutex_lock+0x238/0x488
__mutex_lock_slowpath+0x1c/0x28
mutex_lock+0x50/0x74
clk_prepare_lock+0x7c/0x9c
clk_core_prepare_lock+0x20/0x44
clk_prepare+0x24/0x30
clk_bulk_prepare+0x40/0xb0
mdss_runtime_resume+0x54/0x1c8
pm_generic_runtime_resume+0x30/0x44
__genpd_runtime_resume+0x68/0x7c
genpd_runtime_resume+0x108/0x1f4
__rpm_callback+0x84/0x144
rpm_callback+0x30/0x88
rpm_resume+0x1f4/0x52c
rpm_resume+0x178/0x52c
__pm_runtime_resume+0x58/0x98
__device_attach+0xe0/0x170
device_initial_probe+0x1c/0x28
bus_probe_device+0x3c/0x9c
device_add+0x644/0x814
mipi_dsi_device_register_full+0xe4/0x170
devm_mipi_dsi_device_register_full+0x28/0x70
ti_sn_bridge_probe+0x1dc/0x2c0
auxiliary_bus_probe+0x4c/0x94
really_probe+0xcc/0x2c8
__driver_probe_device+0xa8/0x130
driver_probe_device+0x48/0x110
__device_attach_driver+0xa4/0xcc
bus_for_each_drv+0x8c/0xd8
__device_attach+0xf8/0x170
device_initial_probe+0x1c/0x28
bus_probe_device+0x3c/0x9c
deferred_probe_work_func+0x9c/0xd8
process_one_work+0x148/0x518
worker_thread+0x138/0x350
kthread+0x138/0x1e0
ret_from_fork+0x10/0x20
The first thread is walking the clk tree and calling
clk_pm_runtime_get() to power on devices required to read the clk
hardware via struct clk_ops::is_enabled(). This thread holds the clk
prepare_lock, and is trying to runtime PM resume a device, when it finds
that the device is in the process of resuming so the thread schedule()s
away waiting for the device to finish resuming before continuing. The
second thread is runtime PM resuming the same device, but the runtime
resume callback is calling clk_prepare(), trying to grab the
prepare_lock waiting on the first thread.
This is a classic ABBA deadlock. To properly fix the deadlock, we must
never runtime PM resume or suspend a device with the clk prepare_lock
held. Actually doing that is near impossible today because the global
prepare_lock would have to be dropped in the middle of the tree, the
device runtime PM resumed/suspended, and then the prepare_lock grabbed
again to ensure consistency of the clk tree topology. If anything
changes with the clk tree in the meantime, we've lost and will need to
start the operation all over again.
Luckily, most of the time we're simply incrementing or decrementing the
runtime PM count on an active device, so we don't have the chance to
schedule away with the prepare_lock held. Let's fix this immediate
problem that can be triggered more easily by simply booting on Qualcomm
sc7180.
Introduce a list of clk_core structures that have been registered, or
are in the process of being registered, that require runtime PM to
operate. Iterate this list and call clk_pm_runtime_get() on each of them
without holding the prepare_lock during clk_disable_unused(). This way
we can be certain that the runtime PM state of the devices will be
active and resumed so we can't schedule away while walking the clk tree
with the prepare_lock held. Similarly, call clk_pm_runtime_put() without
the prepare_lock held to properly drop the runtime PM reference. We
remove the calls to clk_pm_runtime_{get,put}() in this path because
they're superfluous now that we know the devices are runtime resumed.
Reported-by: Douglas Anderson <dianders@chromium.org>
Closes: https://lore.kernel.org/all/20220922084322.RFC.2.I375b6b9e0a0a5348962f004beb3dafee6a12dfbb@changeid/ [1]
Closes: https://issuetracker.google.com/328070191
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Fixes: 9a34b45397e5 ("clk: Add support for runtime PM")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20240325184204.745706-5-sboyd@kernel.org
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 9d05ae531c2cff20d5d527f04e28d28e04379929 ]
Initialize this kref once we allocate memory for the struct clk_core so
that we can reuse the release function to free any memory associated
with the structure. This mostly consolidates code, but also clarifies
that the kref lifetime exists once the container structure (struct
clk_core) is allocated instead of leaving it in a half-baked state for
most of __clk_core_init().
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20240325184204.745706-4-sboyd@kernel.org
Stable-dep-of: e581cf5d2162 ("clk: Get runtime PM before walking tree during disable_unused")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 12ca59b91d04df32e41be5a52f0cabba912c11de ]
Currently, the regulator framework informs us before calling into
their unused cleanup paths, which eases at least some debugging. The
same could be beneficial for clocks, so that random shutdowns shortly
after most initcalls are done can be less of a guess.
Add a pr_info before disabling unused clocks to do so.
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230307132928.3887737-1-konrad.dybcio@linaro.org
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Stable-dep-of: e581cf5d2162 ("clk: Get runtime PM before walking tree during disable_unused")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 75061a6ff49ba3482c6319ded0c26e6a526b0967 ]
This list array doesn't change at runtime. Mark it const to move to RO
memory.
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20220217220554.2711696-2-sboyd@kernel.org
Stable-dep-of: e581cf5d2162 ("clk: Get runtime PM before walking tree during disable_unused")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 8358a76cfb47c9a5af627a0c4e7168aa14fa25f6 ]
Removing this assertion lets us move the kref_put() call outside the
prepare_lock section. We don't need to hold the prepare_lock here to
free memory and destroy the clk_core structure. We've already unlinked
the clk from the clk tree and by the time the release function runs
nothing holds a reference to the clk_core anymore so anything with the
pointer can't access the memory that's being freed anyway. Way back in
commit 496eadf821c2 ("clk: Use lockdep asserts to find missing hold of
prepare_lock") we didn't need to have this assertion either.
Fixes: 496eadf821c2 ("clk: Use lockdep asserts to find missing hold of prepare_lock")
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20240325184204.745706-2-sboyd@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit e97fe4901e0f59a0bfd524578fe3768f8ca42428 ]
It is possible for clk_core_get to dereference a NULL in the following
sequence:
clk_core_get()
of_clk_get_hw_from_clkspec()
__of_clk_get_hw_from_provider()
__clk_get_hw()
__clk_get_hw() can return NULL which is dereferenced by clk_core_get() at
hw->core.
Prior to commit dde4eff47c82 ("clk: Look for parents with clkdev based
clk_lookups") the check IS_ERR_OR_NULL() was performed which would have
caught the NULL.
Reading the description of this function it talks about returning NULL but
that cannot be so at the moment.
Update the function to check for hw before dereferencing it and return NULL
if hw is NULL.
Fixes: dde4eff47c82 ("clk: Look for parents with clkdev based clk_lookups")
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Link: https://lore.kernel.org/r/20240302-linux-next-24-03-01-simple-clock-fixes-v1-1-25f348a5982b@linaro.org
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit ceb87a361d0b079ecbc7d2831618c19087f304a9 upstream.
In the possible_parent_show function, ensure proper handling of the return
value from of_clk_get_parent_name to prevent potential issues arising from
a NULL return.
The current implementation invokes seq_puts directly on the result of
of_clk_get_parent_name without verifying the return value, which can lead
to kernel panic if the function returns NULL.
This patch addresses the concern by introducing a check on the return
value of of_clk_get_parent_name. If the return value is not NULL, the
function proceeds to call seq_puts, providing the returned value as
argument.
However, if of_clk_get_parent_name returns NULL, the function provides a
static string as argument, avoiding the panic.
Fixes: 1ccc0ddf046a ("clk: Use seq_puts() in possible_parent_show()")
Reported-by: Philip Daly <pdaly@redhat.com>
Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
Link: https://lore.kernel.org/r/20230921073217.572151-1-alessandro.carminati@gmail.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
