Hi, On Mon, Aug 09, 2021 at 10:12:15AM +0800, Xiaoming Ni wrote: > Semaphore is sleeping lock. Add might_sleep() to down*() family > (with exception of down_trylock()) to detect atomic context sleep. > > Previously discussed with Peter Zijlstra, see link: > https://lore.kernel.org/lkml/20210806082320.GD22037@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > > Signed-off-by: Xiaoming Ni <nixiaoming@xxxxxxxxxx> > Acked-by: Will Deacon <will@xxxxxxxxxx> This patch results in the following traceback on all arm64 boots with EFI BIOS. The problem is only seen with CONFIG_ACPI_PPTT=y, and thus only on arm64. Guenter --- [ 14.048540] BUG: sleeping function called from invalid context at kernel/locking/semaphore.c:163 [ 14.048700] in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 14, name: cpuhp/0 [ 14.048865] 2 locks held by cpuhp/0/14: [ 14.048943] #0: ffff8000125799b0 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x38/0x254 [ 14.049320] #1: ffff8000125799d8 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x38/0x254 [ 14.049523] irq event stamp: 62 [ 14.049580] hardirqs last enabled at (61): [<ffff800010269690>] finish_task_switch.isra.0+0xd0/0x2f0 [ 14.049689] hardirqs last disabled at (62): [<ffff800010313ce8>] generic_exec_single+0x138/0x190 [ 14.049785] softirqs last enabled at (0): [<ffff8000102245d4>] copy_process+0x634/0x1af4 [ 14.049876] softirqs last disabled at (0): [<0000000000000000>] 0x0 [ 14.050299] CPU: 0 PID: 14 Comm: cpuhp/0 Not tainted 5.14.0-01100-gb91db6a0b52e #1 [ 14.050452] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 [ 14.050694] Call trace: [ 14.050753] dump_backtrace+0x0/0x19c [ 14.050839] show_stack+0x1c/0x30 [ 14.050892] dump_stack_lvl+0x9c/0xd8 [ 14.050949] dump_stack+0x1c/0x38 [ 14.050999] ___might_sleep+0x154/0x200 [ 14.051053] __might_sleep+0x54/0x90 [ 14.051106] down_timeout+0x34/0x90 [ 14.051159] acpi_os_wait_semaphore+0x68/0x9c [ 14.051218] acpi_ut_acquire_mutex+0x50/0xbc [ 14.051277] acpi_get_table+0x3c/0xc0 [ 14.051330] acpi_find_last_cache_level+0x44/0x12c [ 14.051391] _init_cache_level+0xd8/0xe4 [ 14.051446] generic_exec_single+0xf8/0x190 [ 14.051502] smp_call_function_single+0x174/0x1e0 [ 14.051561] init_cache_level+0x30/0x60 [ 14.051614] cacheinfo_cpu_online+0x28/0x840 [ 14.051675] cpuhp_invoke_callback+0x168/0x2ac [ 14.051751] cpuhp_thread_fun+0x198/0x254 [ 14.051810] smpboot_thread_fn+0x200/0x2c0 [ 14.051867] kthread+0x164/0x170 [ 14.051921] ret_from_fork+0x10/0x18
