| Message ID | 20230331195733.699708-1-void@manifault.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Enable RCU semantics for task kptrs | expand |
Hello: This series was applied to bpf/bpf-next.git (master) by Alexei Starovoitov <ast@kernel.org>: On Fri, 31 Mar 2023 14:57:30 -0500 you wrote: > In commit 22df776a9a86 ("tasks: Extract rcu_users out of union"), the > 'refcount_t rcu_users' field was extracted out of a union with the > 'struct rcu_head rcu' field. This allows us to use the field for > refcounting struct task_struct with RCU protection, as the RCU callback > no longer flips rcu_users to be nonzero after the callback is scheduled. > > This patch set leverages this to do a few things: > > [...] Here is the summary with links: - [bpf-next,v2,1/3] bpf: Make struct task_struct an RCU-safe type https://git.kernel.org/bpf/bpf-next/c/d02c48fa1139 - [bpf-next,v2,2/3] bpf: Remove now-defunct task kfuncs https://git.kernel.org/bpf/bpf-next/c/f85671c6ef46 - [bpf-next,v2,3/3] bpf,docs: Update documentation to reflect new task kfuncs https://git.kernel.org/bpf/bpf-next/c/db9d479ab59b You are awesome, thank you!
In commit 22df776a9a86 ("tasks: Extract rcu_users out of union"), the 'refcount_t rcu_users' field was extracted out of a union with the 'struct rcu_head rcu' field. This allows us to use the field for refcounting struct task_struct with RCU protection, as the RCU callback no longer flips rcu_users to be nonzero after the callback is scheduled. This patch set leverages this to do a few things: 1. Marks struct task_struct as RCU safe in the verifier, allowing referenced kptr tasks stored in maps to be accessed in an RCU read region without acquiring a reference (with just a NULL check). 2. Makes bpf_task_acquire() a KF_ACQUIRE | KF_RCU | KF_RET_NULL kfunc. 3. Removes bpf_task_kptr_get() and bpf_task_acquire_not_zero(), as they're now redundant with the above two changes. 4. Updates selftests and documentation accordingly. --- Changelog: v1: https://lore.kernel.org/all/20230331005733.406202-1-void@manifault.com/ v1 -> v2: - Remove testcases validating nested trust inheritance. The first version used 'struct task_struct __rcu *parent', but because that field has the __rcu tag it functions differently on gcc and llvm and causes gcc selftests to fail. Alexei is reworking nested trust, anyways so let's leave it off for now (Alexei). David Vernet (3): bpf: Make struct task_struct an RCU-safe type bpf: Remove now-defunct task kfuncs bpf,docs: Update documentation to reflect new task kfuncs Documentation/bpf/kfuncs.rst | 49 ++++++- kernel/bpf/helpers.c | 78 +--------- kernel/bpf/verifier.c | 1 + .../selftests/bpf/prog_tests/task_kfunc.c | 3 +- .../selftests/bpf/progs/rcu_read_lock.c | 9 +- .../selftests/bpf/progs/task_kfunc_common.h | 6 +- .../selftests/bpf/progs/task_kfunc_failure.c | 135 ++++++++---------- .../selftests/bpf/progs/task_kfunc_success.c | 48 +++++-- 8 files changed, 155 insertions(+), 174 deletions(-)