arena qspinlock #8375
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arena qspinlock #8375
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Sync if_xdp.h uapi header to remove following warning: Warning: Kernel ABI header at 'tools/include/uapi/linux/if_xdp.h' differs from latest version at 'include/uapi/linux/if_xdp.h' Fixes: 48eb03d ("xsk: Add TX timestamp and TX checksum offload support") Signed-off-by: Vishal Chourasia <vishalc@linux.ibm.com> Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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Implement queued spin lock algorithm as BPF program for lock words living in BPF arena. The algorithm is copied from kernel/locking/qspinlock.c and adapted for BPF use. We first implement abstract helpers for portable atomics and acquire/release load instructions, by relying on X86_64 presence to elide expensive barriers and rely on implementation details of the JIT, and fall back to slow but correct implementations elsewhere. When support for acquire/release load/stores lands, we can improve this state. Then, the qspinlock algorithm is adapted to remove dependence on multi-word atomics due to lack of support in BPF ISA. For instance, xchg_tail cannot use 16-bit xchg, and needs to be a implemented as a 32-bit try_cmpxchg loop. Loops which are seemingly infinite from verifier PoV are annotated with cond_break. No feedback is given when loops containing cond_break break due to stalling, the arena will basically be corrupt if a deadlock is triggered. This can be changed in the future with a better cancellation primitive for stuck programs, or integrating resilient spin lock support. Only 1024 NR_CPUs are supported. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Add some basic selftests for qspinlock built over BPF arena using cond_break. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
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