Catalin Marinas <catalin.marinas@xxxxxxx> writes: > On Wed, Sep 10, 2025 at 08:46:55PM -0700, Ankur Arora wrote: >> Switch out the conditional load inerfaces used by rqspinlock >> to smp_cond_read_acquire_timeout(). >> This interface handles the timeout check explicitly and does any >> necessary amortization, so use check_timeout() directly. > > It's worth mentioning that the default smp_cond_load_acquire_timeout() > implementation (without hardware support) only spins 200 times instead > of 16K times in the rqspinlock code. That's probably fine but it would > be good to have confirmation from Kumar or Alexei. As Kumar mentions, I'll redefine the count locally in rqspinlock.c to 16k. >> diff --git a/kernel/bpf/rqspinlock.c b/kernel/bpf/rqspinlock.c >> index 5ab354d55d82..4d2c12d131ae 100644 >> --- a/kernel/bpf/rqspinlock.c >> +++ b/kernel/bpf/rqspinlock.c > [...] >> @@ -313,11 +307,8 @@ EXPORT_SYMBOL_GPL(resilient_tas_spin_lock); >> */ >> static DEFINE_PER_CPU_ALIGNED(struct qnode, rqnodes[_Q_MAX_NODES]); >> >> -#ifndef res_smp_cond_load_acquire >> -#define res_smp_cond_load_acquire(v, c) smp_cond_load_acquire(v, c) >> -#endif >> - >> -#define res_atomic_cond_read_acquire(v, c) res_smp_cond_load_acquire(&(v)->counter, (c)) >> +#define res_atomic_cond_read_acquire_timeout(v, c, t) \ >> + smp_cond_load_acquire_timeout(&(v)->counter, (c), (t)) > > BTW, we have atomic_cond_read_acquire() which accesses the 'counter' of > an atomic_t. You might as well add an atomic_cond_read_acquire_timeout() > in atomic.h than open-code the atomic_t internals here. Good point. That also keeps it close to the locking/qspinlock.c use of atomic_cond_read_acquire(). Will add atomic_cond_read_acquire_timeout() (and other variants that we define in include/linux/atomic.h). > Otherwise the patch looks fine to me, much simpler than the previous > attempt. > > Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> Thanks! -- ankur
