| Message ID | 20211223031207.556189-1-chi.minghao@zte.com.cn |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] ipc/sem: do not sleep with a spin lock held | expand |
On 23. 12. 21, 4:12, cgel.zte@gmail.com wrote: > From: Minghao Chi <chi.minghao@zte.com.cn> > > We can't call kvfree() with a spin lock held, so defer it. Sorry, defer what? There are attempts to fix kvfree instead, not sure which of these approaches (fix kvfree or its callers) won in the end? > Fixes: fc37a3b8b438 ("[PATCH] ipc sem: use kvmalloc for sem_undo > allocation") > > Reported-by: Zeal Robot <zealci@zte.com.cn> > Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn> > --- > changelog since v2: > + Fixes: fc37a3b8b438 ("[PATCH] ipc sem: use kvmalloc for sem_undo > + allocation") > ipc/sem.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/ipc/sem.c b/ipc/sem.c > index 6693daf4fe11..0dbdb98fdf2d 100644 > --- a/ipc/sem.c > +++ b/ipc/sem.c > @@ -1964,6 +1964,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) > */ > un = lookup_undo(ulp, semid); > if (un) { > + spin_unlock(&ulp->lock); > kvfree(new); > goto success; > }
Hi Jiri, On 1/3/22 10:27, Jiri Slaby wrote: > On 23. 12. 21, 4:12, cgel.zte@gmail.com wrote: >> From: Minghao Chi <chi.minghao@zte.com.cn> >> >> We can't call kvfree() with a spin lock held, so defer it. > > Sorry, defer what? > First drop the spinlock, then call kvfree(). > There are attempts to fix kvfree instead, not sure which of these > approaches (fix kvfree or its callers) won in the end? > Exactly. We have three options - but noone volunteered yet to decide: - change ipc/sem.c [minimal change] - change kvfree() to use vfree_atomic() [would also fix other changes that did s/kfree/kvfree/] - Modify the vma handling so that it becomes safe to call vfree() while holding a spinlock. [perfect approach, but I'm concerned about side effects] -- Manfred
On Wed, Dec 22, 2021 at 7:12 PM <cgel.zte@gmail.com> wrote: > > From: Minghao Chi <chi.minghao@zte.com.cn> > > We can't call kvfree() with a spin lock held, so defer it. > Fixes: fc37a3b8b438 ("[PATCH] ipc sem: use kvmalloc for sem_undo > allocation") > > Reported-by: Zeal Robot <zealci@zte.com.cn> > Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn> Reviewed-by: Shakeel Butt <shakeelb@google.com>
On 1/4/22 19:20, Shakeel Butt wrote: > On Wed, Dec 22, 2021 at 7:12 PM <cgel.zte@gmail.com> wrote: >> From: Minghao Chi <chi.minghao@zte.com.cn> >> >> We can't call kvfree() with a spin lock held, so defer it. >> Fixes: fc37a3b8b438 ("[PATCH] ipc sem: use kvmalloc for sem_undo >> allocation") >> >> Reported-by: Zeal Robot <zealci@zte.com.cn> >> Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn> > Reviewed-by: Shakeel Butt <shakeelb@google.com> Reviewed-by: Manfred Spraul <manfred@colorfullife.com> -- Manfred
diff --git a/ipc/sem.c b/ipc/sem.c index 6693daf4fe11..0dbdb98fdf2d 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -1964,6 +1964,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) */ un = lookup_undo(ulp, semid); if (un) { + spin_unlock(&ulp->lock); kvfree(new); goto success; } @@ -1976,9 +1977,8 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) ipc_assert_locked_object(&sma->sem_perm); list_add(&new->list_id, &sma->list_id); un = new; - -success: spin_unlock(&ulp->lock); +success: sem_unlock(sma, -1); out: return un;