On 15/10/2018 14:52, Dmitry Osipenko wrote: > On 10/15/18 3:52 PM, Jon Hunter wrote: >> >> On 30/08/18 19:36, Dmitry Osipenko wrote: >>> This fixes splats like the one below if CONFIG_DEBUG_ATOMIC_SLEEP=y >>> and machine (Tegra30) booted with SMP=n or all secondary CPU's are put >>> offline. >>> >>> BUG: sleeping function called from invalid context at >>> kernel/locking/mutex.c:254 >>> in_atomic(): 1, irqs_disabled(): 128, pid: 0, name: swapper/0 >>> CPU: 0 PID: 0 Comm: swapper/0 Tainted: G C >>> 4.18.0-next-20180821-00180-gc3ebb6544e44-dirty #823 >>> Hardware name: NVIDIA Tegra SoC (Flattened Device Tree) >>> [<c01134f4>] (unwind_backtrace) from [<c010db2c>] (show_stack+0x20/0x24) >>> [<c010db2c>] (show_stack) from [<c0bd0f3c>] (dump_stack+0x94/0xa8) >>> [<c0bd0f3c>] (dump_stack) from [<c0151df8>] (___might_sleep+0x13c/0x174) >>> [<c0151df8>] (___might_sleep) from [<c0151ea0>] (__might_sleep+0x70/0xa8) >>> [<c0151ea0>] (__might_sleep) from [<c0bec2b8>] (mutex_lock+0x2c/0x70) >>> [<c0bec2b8>] (mutex_lock) from [<c0589844>] >>> (tegra_powergate_is_powered+0x44/0xa8) >>> [<c0589844>] (tegra_powergate_is_powered) from [<c0581a60>] >>> (tegra30_cpu_rail_off_ready+0x30/0x74) >>> [<c0581a60>] (tegra30_cpu_rail_off_ready) from [<c0122244>] >>> (tegra30_idle_lp2+0xa0/0x108) >>> [<c0122244>] (tegra30_idle_lp2) from [<c0853438>] >>> (cpuidle_enter_state+0x140/0x540) >>> [<c0853438>] (cpuidle_enter_state) from [<c08538a4>] >>> (cpuidle_enter+0x40/0x4c) >>> [<c08538a4>] (cpuidle_enter) from [<c01595e0>] (call_cpuidle+0x30/0x48) >>> [<c01595e0>] (call_cpuidle) from [<c01599f8>] (do_idle+0x238/0x28c) >>> [<c01599f8>] (do_idle) from [<c0159d28>] (cpu_startup_entry+0x28/0x2c) >>> [<c0159d28>] (cpu_startup_entry) from [<c0be76c8>] (rest_init+0xd8/0xdc) >>> [<c0be76c8>] (rest_init) from [<c1200f50>] (start_kernel+0x41c/0x430) >> >> Given the above, rather than converting to a spinlock I wonder if we are >> just better off dropping the mutex completely from >> tegra_powergate_is_powered()? Otherwise ... >> >>> Signed-off-by: Dmitry Osipenko <dig...@gmail.com> >>> --- >>> drivers/soc/tegra/pmc.c | 36 ++++++++++++++++++------------------ >>> 1 file changed, 18 insertions(+), 18 deletions(-) >>> >>> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c >>> index 2d6f3fcf3211..d6bc9f66f1cd 100644 >>> --- a/drivers/soc/tegra/pmc.c >>> +++ b/drivers/soc/tegra/pmc.c >>> @@ -186,7 +186,7 @@ struct tegra_pmc_soc { >>> * @lp0_vec_phys: physical base address of the LP0 warm boot code >>> * @lp0_vec_size: size of the LP0 warm boot code >>> * @powergates_available: Bitmap of available power gates >>> - * @powergates_lock: mutex for power gate register access >>> + * @powergates_lock: lock for power gate register access >>> */ >>> struct tegra_pmc { >>> struct device *dev; >>> @@ -215,7 +215,7 @@ struct tegra_pmc { >>> u32 lp0_vec_size; >>> DECLARE_BITMAP(powergates_available, TEGRA_POWERGATE_MAX); >>> >>> - struct mutex powergates_lock; >>> + spinlock_t powergates_lock; >>> }; >>> >>> static struct tegra_pmc *pmc = &(struct tegra_pmc) { >>> @@ -288,10 +288,10 @@ static int tegra_powergate_set(unsigned int id, bool >>> new_state) >>> if (id == TEGRA_POWERGATE_3D && pmc->soc->has_gpu_clamps) >>> return -EINVAL; >>> >>> - mutex_lock(&pmc->powergates_lock); >>> + spin_lock(&pmc->powergates_lock); >>> >>> if (tegra_powergate_state(id) == new_state) { >>> - mutex_unlock(&pmc->powergates_lock); >>> + spin_unlock(&pmc->powergates_lock); >>> return 0; >>> } >>> >>> @@ -300,7 +300,7 @@ static int tegra_powergate_set(unsigned int id, bool >>> new_state) >>> err = readx_poll_timeout(tegra_powergate_state, id, status, >>> status == new_state, 10, 100000); >>> >>> - mutex_unlock(&pmc->powergates_lock); >>> + spin_unlock(&pmc->powergates_lock); >> >> ... the above readx_poll_timeout needs to be converted to the atomic >> version. Furthermore, the above 100ms timeout is probably not suited to >> spinlock. > > It's converted in the second patch. Seems mutex indeed could be dropped from > tegra_powergate_is_powered, at least for now I can't recall why decided to > keep the locking. Thank you for the review, I'll try to drop the mutex and > come back with v2 if it will be fine.
Sorry if you were waiting for my response, but yes sounds good to me. Cheers Jon -- nvpublic