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[109.252.91.118]) by smtp.googlemail.com with ESMTPSA id h2-v6sm2202707lfb.27.2018.10.15.06.52.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 15 Oct 2018 06:52:16 -0700 (PDT) Subject: Re: [PATCH v1 1/2] soc/tegra: pmc: Turn powergates_lock into spinlock To: Jon Hunter , Thierry Reding Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <20180830183635.4474-1-digetx@gmail.com> <7369869e-e58f-3760-d428-b00fb9cd28d9@nvidia.com> From: Dmitry Osipenko Message-ID: <57c3b1a6-0a60-613e-a4e7-5d66c199b860@gmail.com> Date: Mon, 15 Oct 2018 16:52:15 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <7369869e-e58f-3760-d428-b00fb9cd28d9@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) >> [] (unwind_backtrace) from [] (show_stack+0x20/0x24) >> [] (show_stack) from [] (dump_stack+0x94/0xa8) >> [] (dump_stack) from [] (___might_sleep+0x13c/0x174) >> [] (___might_sleep) from [] (__might_sleep+0x70/0xa8) >> [] (__might_sleep) from [] (mutex_lock+0x2c/0x70) >> [] (mutex_lock) from [] (tegra_powergate_is_powered+0x44/0xa8) >> [] (tegra_powergate_is_powered) from [] (tegra30_cpu_rail_off_ready+0x30/0x74) >> [] (tegra30_cpu_rail_off_ready) from [] (tegra30_idle_lp2+0xa0/0x108) >> [] (tegra30_idle_lp2) from [] (cpuidle_enter_state+0x140/0x540) >> [] (cpuidle_enter_state) from [] (cpuidle_enter+0x40/0x4c) >> [] (cpuidle_enter) from [] (call_cpuidle+0x30/0x48) >> [] (call_cpuidle) from [] (do_idle+0x238/0x28c) >> [] (do_idle) from [] (cpu_startup_entry+0x28/0x2c) >> [] (cpu_startup_entry) from [] (rest_init+0xd8/0xdc) >> [] (rest_init) from [] (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 >> --- >> 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.