On 20/07/17 17:28, Michał Mirosław wrote: > On Thu, Jul 20, 2017 at 01:45:12PM +0100, Jon Hunter wrote: >> >> On 20/07/17 01:29, Michał Mirosław wrote: >>> This removes unnecessary lock causing following BUG splat: >>> >>> BUG: sleeping function called from invalid context at /linux/kernel/locking/mutex.c:747 >>> in_atomic(): 1, irqs_disabled(): 128, pid: 0, name: swapper/0 >>> no locks held by swapper/0/0. >>> CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 4.13.0-rc1mq-00016-gbf3f627c6b2b #1 >>> Hardware name: NVIDIA Tegra SoC (Flattened Device Tree) >>> [<b0110a14>] (unwind_backtrace) from [<b010c710>] (show_stack+0x18/0x1c) >>> [<b010c710>] (show_stack) from [<b068ada8>] (dump_stack+0x84/0x98) >>> [<b068ada8>] (dump_stack) from [<b014ff54>] (___might_sleep+0x158/0x17c) >>> [<b014ff54>] (___might_sleep) from [<b06a15c4>] (__mutex_lock+0x34/0x9a0) >>> [<b06a15c4>] (__mutex_lock) from [<b06a30dc>] (mutex_lock_nested+0x24/0x2c) >>> [<b06a30dc>] (mutex_lock_nested) from [<b041f6d8>] (tegra_powergate_is_powered+0x40/0xa4) >>> [<b041f6d8>] (tegra_powergate_is_powered) from [<b04197e8>] (tegra30_cpu_rail_off_ready+0x28/0x6c) >>> [<b04197e8>] (tegra30_cpu_rail_off_ready) from [<b011c73c>] (tegra30_idle_lp2+0x70/0x114) >>> [<b011c73c>] (tegra30_idle_lp2) from [<b0516080>] (cpuidle_enter_state+0x12c/0x47c) >>> [<b0516080>] (cpuidle_enter_state) from [<b0163394>] (do_idle+0x1b4/0x204) >>> [<b0163394>] (do_idle) from [<b016368c>] (cpu_startup_entry+0x20/0x24) >>> [<b016368c>] (cpu_startup_entry) from [<b0900dd8>] (start_kernel+0x39c/0x3a8) >>> >>> Signed-off-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx> >>> --- >>> drivers/soc/tegra/pmc.c | 2 -- >>> 1 file changed, 2 deletions(-) >>> >>> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c >>> index e233dd5dcab3..3e6ec9fdba41 100644 >>> --- a/drivers/soc/tegra/pmc.c >>> +++ b/drivers/soc/tegra/pmc.c >>> @@ -526,9 +526,7 @@ int tegra_powergate_is_powered(unsigned int id) >>> if (!tegra_powergate_is_valid(id)) >>> return -EINVAL; >>> >>> - mutex_lock(&pmc->powergates_lock); >>> status = tegra_powergate_state(id); >>> - mutex_unlock(&pmc->powergates_lock); >>> >>> return status; >>> } >> >> Thanks for the fix. However, I would prefer that we fix this the following >> way ... >> >> diff --git a/drivers/clk/tegra/clk-tegra30.c b/drivers/clk/tegra/clk-tegra30.c >> index a2d163f759b4..546d2b121c39 100644 >> --- a/drivers/clk/tegra/clk-tegra30.c >> +++ b/drivers/clk/tegra/clk-tegra30.c >> @@ -1152,9 +1152,9 @@ static bool tegra30_cpu_rail_off_ready(void) >> >> cpu_rst_status = readl(clk_base + >> TEGRA30_CLK_RST_CONTROLLER_CPU_CMPLX_STATUS); >> - cpu_pwr_status = tegra_powergate_is_powered(TEGRA_POWERGATE_CPU1) || >> - tegra_powergate_is_powered(TEGRA_POWERGATE_CPU2) || >> - tegra_powergate_is_powered(TEGRA_POWERGATE_CPU3); >> + cpu_pwr_status = tegra_pmc_cpu_is_powered(1) || >> + tegra_pmc_cpu_is_powered(2) || >> + tegra_pmc_cpu_is_powered(3); >> >> if (((cpu_rst_status & 0xE) != 0xE) || cpu_pwr_status) >> return false; >> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c >> index e233dd5dcab3..f61371ea3fe0 100644 >> --- a/drivers/soc/tegra/pmc.c >> +++ b/drivers/soc/tegra/pmc.c >> @@ -605,7 +605,7 @@ bool tegra_pmc_cpu_is_powered(unsigned int cpuid) >> if (id < 0) >> return false; >> >> - return tegra_powergate_is_powered(id); >> + return tegra_powergate_state(id); >> } >> >> >> Could you try the above and make sure that this works? > > Something ate TABs in your patch, but yes, it works. > >> I would prefer to leave the mutex in tegra_powergate_is_powered() so it could >> be used by any driver. Or maybe we could even get rid of >> tegra_powergate_is_powered() if we don't really need it. > > This mutex does not protect anything here, though - there is only one register > read inside the locked section, and after unlock other CPU might change > it before the read value gets returned. > > Code size-wise it would be better to remove tegra_pmc_cpu_is_powered() > instead. Maybe, but tegra_pmc_cpu_is_powered() is needed by tegra30_boot_secondary(). Jon -- nvpublic -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
