mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-08-31 05:49:47 -04:00
b3134b8c1a
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 <conor@kernel.org>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Fixes: ab83647fad ("riscv: Add qspinlock support")
Link: https://lore.kernel.org/linux-riscv/CAJF2gTQwYTGinBmCSgVUoPv0_q4EPt_+WiyfUA1HViAKgUzxAg@mail.gmail.com/T/#mf488e6347817fca03bb93a7d34df33d8615b3775
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Tested-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Tested-by: Nam Cao <namcao@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20241130153310.3349484-1-guoren@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.