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queued_spin_lock_slowpath() and queued_spin_unlock() are dispatched through pv_ops_lock via the paravirt-ops ALTERNATIVE machinery, which picks the target (native inline store / hypervisor call) once at boot and cannot change at runtime. Convert both to static_call(). The site becomes a direct call patched in place (one byte smaller), and on native the unlock still collapses to the inline "movb $0, (%rdi)" store, so the fast path is unchanged. Unlike the ALTERNATIVE mechanism, a static_call() target can also be updated at runtime via static_call_update(). This is a prerequisite for the contended_release tracepoint, which has to swap in a traced unlock while the system is running. [ ilvokhin: commit message; fix PARAVIRT_SPINLOCKS=n build; teach __static_call_validate() about the inline unlock insn; make the slowpath site module-safe: static_call_mod() + EXPORT_STATIC_CALL_TRAMP(); pass @lock to the callee-save unlock, fixing a boot hang under CALL_DEPTH_TRACKING. Boot tested native + KVM PV guest. ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Co-developed-by: Dmitry Ilvokhin <d@ilvokhin.com> Signed-off-by: Dmitry Ilvokhin <d@ilvokhin.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Juergen Gross <jgross@suse.com> Link: https://lore.kernel.org/all/20260603120811.GW3493090@noisy.programming.kicks-ass.net/ Link: https://patch.msgid.link/9a32ae399eb804a02a31af04dcabe7e7ee4f3fdf.1785778551.git.d@ilvokhin.com |
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