> On Oct 4, 2023, at 8:23 PM, Song Liu <song@xxxxxxxxxx> wrote: > > htab_lock_bucket uses the following logic to avoid recursion: > > 1. preempt_disable(); > 2. check percpu counter htab->map_locked[hash] for recursion; > 2.1. if map_lock[hash] is already taken, return -BUSY; > 3. raw_spin_lock_irqsave(); > > However, if an IRQ hits between 2 and 3, BPF programs attached to the IRQ > logic will not able to access the same hash of the hashtab and get -EBUSY. > This -EBUSY is not really necessary. Fix it by disabling IRQ before > checking map_locked: > > 1. preempt_disable(); > 2. local_irq_save(); > 3. check percpu counter htab->map_locked[hash] for recursion; > 3.1. if map_lock[hash] is already taken, return -BUSY; > 4. raw_spin_lock(). > > Similarly, use raw_spin_unlock() and local_irq_restore() in > htab_unlock_bucket(). > > Suggested-by: Tejun Heo <tj@xxxxxxxxxx> > Signed-off-by: Song Liu <song@xxxxxxxxxx> Somehow this didn't make to lore and thus not to patchwork. Let me resend, sorry for the noise. Song
