diff options
| author | Stafford Horne <shorne@gmail.com> | 2020-06-26 05:24:24 +0900 |
|---|---|---|
| committer | Stafford Horne <shorne@gmail.com> | 2020-08-04 10:59:45 +0900 |
| commit | d0b7213f895cd0e209ff5ba89998aeb09267bdc7 (patch) | |
| tree | 9ab81b1006a57fb1043816b60ed8f1599368a813 | |
| parent | 9e9da64124ff37e064a75fabdbd6010787a1e0ea (diff) | |
init: Align init_task to avoid conflict with MUTEX_FLAGS
When booting on 32-bit machines (seen on OpenRISC) I saw this warning
with CONFIG_DEBUG_MUTEXES turned on.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at kernel/locking/mutex.c:1242 __mutex_unlock_slowpath+0x328/0x3ec
DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current)
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.8.0-rc1-simple-smp-00005-g2864e2171db4-dirty #179
Call trace:
[<(ptrval)>] dump_stack+0x34/0x48
[<(ptrval)>] __warn+0x104/0x158
[<(ptrval)>] ? __mutex_unlock_slowpath+0x328/0x3ec
[<(ptrval)>] warn_slowpath_fmt+0x7c/0x94
[<(ptrval)>] __mutex_unlock_slowpath+0x328/0x3ec
[<(ptrval)>] mutex_unlock+0x18/0x28
[<(ptrval)>] __cpuhp_setup_state_cpuslocked.part.0+0x29c/0x2f4
[<(ptrval)>] ? page_alloc_cpu_dead+0x0/0x30
[<(ptrval)>] ? start_kernel+0x0/0x684
[<(ptrval)>] __cpuhp_setup_state+0x4c/0x5c
[<(ptrval)>] page_alloc_init+0x34/0x68
[<(ptrval)>] ? start_kernel+0x1a0/0x684
[<(ptrval)>] ? early_init_dt_scan_nodes+0x60/0x70
irq event stamp: 0
I traced this to kernel/locking/mutex.c storing 3 bits of MUTEX_FLAGS in
the task_struct pointer (mutex.owner). There is a comment saying that
task_structs are always aligned to L1_CACHE_BYTES. This is not true for
the init_task.
On 64-bit machines this is not a problem because symbol addresses are
naturally aligned to 64-bits providing 3 bits for MUTEX_FLAGS. Howerver,
for 32-bit machines the symbol address only has 2 bits available.
Fix this by setting init_task alignment to at least L1_CACHE_BYTES.
Signed-off-by: Stafford Horne <shorne@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
| -rw-r--r-- | init/init_task.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/init/init_task.c b/init/init_task.c index 15089d15010a..ab6173f8e6a8 100644 --- a/init/init_task.c +++ b/init/init_task.c @@ -65,6 +65,7 @@ struct task_struct init_task #ifdef CONFIG_ARCH_TASK_STRUCT_ON_STACK __init_task_data #endif + __aligned(L1_CACHE_BYTES) = { #ifdef CONFIG_THREAD_INFO_IN_TASK .thread_info = INIT_THREAD_INFO(init_task), |