From: Guo Ren Date: Sat, 30 Nov 2024 15:33:10 +0000 (-0500) Subject: riscv: Fixup boot failure when CONFIG_DEBUG_RT_MUTEXES=y X-Git-Tag: v6.13-rc3~28^2~3 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b3134b8c1a1cf5779a74df902c75fa185083006e;p=thirdparty%2Fkernel%2Flinux.git riscv: Fixup boot failure when CONFIG_DEBUG_RT_MUTEXES=y When CONFIG_DEBUG_RT_MUTEXES=y, mutex_lock->rt_mutex_try_acquire would change from rt_mutex_cmpxchg_acquire to rt_mutex_slowtrylock(): raw_spin_lock_irqsave(&lock->wait_lock, flags); ret = __rt_mutex_slowtrylock(lock); raw_spin_unlock_irqrestore(&lock->wait_lock, flags); Because queued_spin_#ops to ticket_#ops is changed one by one by jump_label, raw_spin_lock/unlock would cause a deadlock during the changing. That means in arch/riscv/kernel/jump_label.c: 1. arch_jump_label_transform_queue() -> mutex_lock(&text_mutex); +-> raw_spin_lock -> queued_spin_lock |-> raw_spin_unlock -> queued_spin_unlock patch_insn_write -> change the raw_spin_lock to ticket_lock mutex_unlock(&text_mutex); ... 2. /* Dirty the lock value */ arch_jump_label_transform_queue() -> mutex_lock(&text_mutex); +-> raw_spin_lock -> *ticket_lock* |-> raw_spin_unlock -> *queued_spin_unlock* /* BUG: ticket_lock with queued_spin_unlock */ patch_insn_write -> change the raw_spin_unlock to ticket_unlock mutex_unlock(&text_mutex); ... 3. /* Dead lock */ arch_jump_label_transform_queue() -> mutex_lock(&text_mutex); +-> raw_spin_lock -> ticket_lock /* deadlock! */ |-> raw_spin_unlock -> ticket_unlock patch_insn_write -> change other raw_spin_#op -> ticket_#op mutex_unlock(&text_mutex); So, the solution is to disable mutex usage of arch_jump_label_transform_queue() during early_boot_irqs_disabled, just like we have done for stop_machine. Reported-by: Conor Dooley Signed-off-by: Guo Ren Signed-off-by: Guo Ren Fixes: ab83647fadae ("riscv: Add qspinlock support") Link: https://lore.kernel.org/linux-riscv/CAJF2gTQwYTGinBmCSgVUoPv0_q4EPt_+WiyfUA1HViAKgUzxAg@mail.gmail.com/T/#mf488e6347817fca03bb93a7d34df33d8615b3775 Cc: Palmer Dabbelt Cc: Alexandre Ghiti Tested-by: Conor Dooley Reviewed-by: Alexandre Ghiti Tested-by: Alexandre Ghiti Tested-by: Nam Cao Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20241130153310.3349484-1-guoren@kernel.org Signed-off-by: Palmer Dabbelt --- diff --git a/arch/riscv/kernel/jump_label.c b/arch/riscv/kernel/jump_label.c index 6eee6f736f687..654ed159c830b 100644 --- a/arch/riscv/kernel/jump_label.c +++ b/arch/riscv/kernel/jump_label.c @@ -36,9 +36,15 @@ bool arch_jump_label_transform_queue(struct jump_entry *entry, insn = RISCV_INSN_NOP; } - mutex_lock(&text_mutex); - patch_insn_write(addr, &insn, sizeof(insn)); - mutex_unlock(&text_mutex); + if (early_boot_irqs_disabled) { + riscv_patch_in_stop_machine = 1; + patch_insn_write(addr, &insn, sizeof(insn)); + riscv_patch_in_stop_machine = 0; + } else { + mutex_lock(&text_mutex); + patch_insn_write(addr, &insn, sizeof(insn)); + mutex_unlock(&text_mutex); + } return true; }