From: Mike Rapoport <[email protected]>
Since the commit a148866489fb ("sched: Replace rq::wake_list")
task_struct and CSD_TYPE_TTWU objects can be on the same queue and this
requires that have layout similar enough.
This assumption is broken when CONFIG_GCC_PLUGIN_RANDSTRUCT is enabled:
CHK include/generated/compile.h
CC kernel/smp.o
In file included from arch/x86/include/asm/atomic.h:5,
from include/linux/atomic.h:7,
from include/linux/llist.h:51,
from include/linux/irq_work.h:5,
from kernel/smp.c:10:
kernel/smp.c: In function ‘smp_init’:
include/linux/compiler.h:392:38: error: call to ‘__compiletime_assert_157’
declared with attribute error: BUILD_BUG_ON failed: offsetof(struct
task_struct, wake_entry_type) - offsetof(struct task_struct, wake_entry) !=
offsetof(struct __call_single_data, flags) - offsetof(struct
__call_single_data, llist)
392 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^
include/linux/compiler.h:373:4: note: in definition of macro
‘__compiletime_assert’
373 | prefix ## suffix(); \
| ^~~~~~
include/linux/compiler.h:392:2: note: in expansion of macro
‘_compiletime_assert’
392 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro
‘compiletime_assert’
39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
| ^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:50:2: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
| ^~~~~~~~~~~~~~~~
kernel/smp.c:687:2: note: in expansion of macro ‘BUILD_BUG_ON’
687 | BUILD_BUG_ON(offsetof(struct task_struct, wake_entry_type) -
offsetof(struct task_struct, wake_entry) !=
| ^~~~~~~~~~~~
Wrap 'wake_entry' and 'wake_entry_type' fiels of task_struct in an
anonymous struct to keep their relative layout intact during
randomization.
Suggested-by: Steven Rostedt <[email protected]>
Signed-off-by: Mike Rapoport <[email protected]>
---
v2: use anonymous struct as Steven suggested.
include/linux/sched.h | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b62e6aaf28f0..7e30a09df616 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -654,8 +654,15 @@ struct task_struct {
unsigned int ptrace;
#ifdef CONFIG_SMP
- struct llist_node wake_entry;
- unsigned int wake_entry_type;
+ /*
+ * The layout of these fields must match the layout of CSD_TYPE_TTWU
+ * so they can be on the same @call_single_queue
+ */
+ struct {
+ struct llist_node wake_entry;
+ unsigned int wake_entry_type;
+ };
+
int on_cpu;
#ifdef CONFIG_THREAD_INFO_IN_TASK
/* Current CPU: */
--
2.25.4
