On 2024-12-04 08:42:23 [-0300], Wander Lairson Costa wrote: > This is the second attempt at fixing the behavior of igb_msix_other() > for PREEMPT_RT. The previous attempt [1] was reverted [2] following > concerns raised by Sebastian [3]. > > The initial approach proposed converting vfs_lock to a raw_spinlock, > a minor change intended to make it safe. However, it became evident > that igb_rcv_msg_from_vf() invokes kcalloc with GFP_ATOMIC, > which is unsafe in interrupt context on PREEMPT_RT systems. > > To address this, the solution involves splitting igb_msg_task() > into two parts: > > * One part invoked from the IRQ context. > * Another part called from the threaded interrupt handler. > > To accommodate this, vfs_lock has been restructured into a double > lock: a spinlock_t and a raw_spinlock_t. In the revised design: > > * igb_disable_sriov() locks both spinlocks. > * Each part of igb_msg_task() locks the appropriate spinlock for > its execution context.
- Is this limited to PREEMPT_RT or does it also occur on PREEMPT systems with threadirqs? And if this is PREEMPT_RT only, why? - What causes the failure? I see you reworked into two parts to behave similar to what happens without threaded interrupts. There is still no explanation for it. Is there a timing limit or was there another register operation which removed the mailbox message? > Cheers, > Wander Sebastian
