Following changes will implement fine-grained range locks for the
MM locking API, using a data structure to represent the existing
locks, and a mutex to protect that data structure.
As a result, we need to prepare for the possibility that unlocking
a memory range may need to sleep when acquiring that mutex.
Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
---
kernel/bpf/stackmap.c | 6 +++++-
kernel/exit.c | 2 +-
mm/mm_lock_rwsem_checked.c | 3 +++
3 files changed, 9 insertions(+), 2 deletions(-)
diff --git kernel/bpf/stackmap.c kernel/bpf/stackmap.c
index ba2399ce00e4..0f483abeb94c 100644
--- kernel/bpf/stackmap.c
+++ kernel/bpf/stackmap.c
@@ -308,8 +308,12 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
*
* Same fallback is used for kernel stack (!user) on a stackmap
* with build_id.
+ *
+ * FIXME - currently disabling the build_id lookup feature
+ * as mm_read_range_unlock() may block, which is not always
+ * possible to do here.
*/
- if (!user || !current || !current->mm || irq_work_busy ||
+ if (true || !user || !current || !current->mm || irq_work_busy ||
!mm_read_range_trylock(current->mm, mm_range_ptr)) {
/* cannot access current->mm, fall back to ips */
for (i = 0; i < trace_nr; i++) {
diff --git kernel/exit.c kernel/exit.c
index 9a0b72562adb..60ec6efb4e2c 100644
--- kernel/exit.c
+++ kernel/exit.c
@@ -478,9 +478,9 @@ static void exit_mm(void)
/* more a memory barrier than a real lock */
task_lock(current);
current->mm = NULL;
- mm_read_unlock(mm);
enter_lazy_tlb(mm, current);
task_unlock(current);
+ mm_read_unlock(mm);
mm_update_next_owner(mm);
mmput(mm);
if (test_thread_flag(TIF_MEMDIE))
diff --git mm/mm_lock_rwsem_checked.c mm/mm_lock_rwsem_checked.c
index 3551deb85e3d..e45d1a598c87 100644
--- mm/mm_lock_rwsem_checked.c
+++ mm/mm_lock_rwsem_checked.c
@@ -61,6 +61,7 @@ EXPORT_SYMBOL(mm_write_range_trylock);
void mm_write_range_unlock(struct mm_struct *mm, struct mm_lock_range *range)
{
+ might_sleep();
if (range->mm != mm)
mm_lock_dump("mm_write_range_unlock");
range->mm = NULL;
@@ -113,6 +114,7 @@ EXPORT_SYMBOL(mm_read_range_trylock);
void mm_read_range_unlock(struct mm_struct *mm, struct mm_lock_range *range)
{
+ might_sleep();
if (range->mm != mm)
mm_lock_dump("mm_read_range_unlock");
range->mm = NULL;
@@ -123,6 +125,7 @@ EXPORT_SYMBOL(mm_read_range_unlock);
void mm_read_range_unlock_non_owner(struct mm_struct *mm,
struct mm_lock_range *range)
{
+ might_sleep();
if (range->mm != mm)
mm_lock_dump("mm_read_range_unlock_non_owner");
range->mm = NULL;
--
2.25.0.341.g760bfbb309-goog
