Commits
Jiada Wang committed 2071ac985d3
PM / Domains: Avoid a potential deadlock
Lockdep warns that prepare_lock and genpd->mlock can cause a deadlock
the deadlock scenario is like following:
First thread is probing cs2000
cs2000_probe()
clk_register()
__clk_core_init()
clk_prepare_lock() ----> acquires prepare_lock
cs2000_recalc_rate()
i2c_smbus_read_byte_data()
rcar_i2c_master_xfer()
dma_request_chan()
rcar_dmac_of_xlate()
rcar_dmac_alloc_chan_resources()
pm_runtime_get_sync()
__pm_runtime_resume()
rpm_resume()
rpm_callback()
genpd_runtime_resume() ----> acquires genpd->mlock
Second thread is attaching any device to the same PM domain
genpd_add_device()
genpd_lock() ----> acquires genpd->mlock
cpg_mssr_attach_dev()
of_clk_get_from_provider()
__of_clk_get_from_provider()
__clk_create_clk()
clk_prepare_lock() ----> acquires prepare_lock
Since currently no PM provider access genpd's critical section
in .attach_dev, and .detach_dev callbacks, so there is no need to protect
these two callbacks with genpd->mlock.
This patch avoids a potential deadlock by moving out .attach_dev and .detach_dev
from genpd->mlock, so that genpd->mlock won't be held when prepare_lock is acquired
in .attach_dev and .detach_dev
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>