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| author |   Paul E. McKenney <paulmck@kernel.org> | 2022-05-23 20:50:11 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2022-06-20 09:22:27 -0700 |
| commit | 3847b64570b1753e9863a4106aec03f4d68e7b17 (patch) | |
| tree | f2ff9588ddb2952f984004b86368b694b24300a8 /include/linux/rcupdate.h | |
| parent | rcu-tasks: Drive synchronous grace periods from calling task (diff) | |
| download | linux-dev-3847b64570b1753e9863a4106aec03f4d68e7b17.tar.xz linux-dev-3847b64570b1753e9863a4106aec03f4d68e7b17.zip | |
rcu-tasks: Merge state into .b.need_qs and atomically update
This commit gets rid of the task_struct structure's ->trc_reader_checked
field, making it instead be a bit within the task_struct structure's
existing ->trc_reader_special.b.need_qs field. This commit also
atomically loads, stores, and checks the resulting combination of the
reader-checked and need-quiescent state flags. This will in turn allow
significant simplification of the rcu_tasks_trace_postgp() function
as well as elimination of the trc_n_readers_need_end counter in later
commits. These changes will in turn simplify later elimination of the
RCU Tasks Trace scan of the task list, which will make RCU Tasks Trace
grace periods less CPU-intensive.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: KP Singh <kpsingh@kernel.org>
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 1a32036c918c..1e728d544fc1 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -169,13 +169,17 @@ void synchronize_rcu_tasks(void); # endif # ifdef CONFIG_TASKS_TRACE_RCU -# define rcu_tasks_trace_qs(t) \ - do { \ - if (!likely(READ_ONCE((t)->trc_reader_checked)) && \ - !unlikely(READ_ONCE((t)->trc_reader_nesting))) { \ - smp_store_release(&(t)->trc_reader_checked, true); \ - smp_mb(); /* Readers partitioned by store. */ \ - } \ +// Bits for ->trc_reader_special.b.need_qs field. +#define TRC_NEED_QS 0x1 // Task needs a quiescent state. +#define TRC_NEED_QS_CHECKED 0x2 // Task has been checked for needing quiescent state. + +u8 rcu_trc_cmpxchg_need_qs(struct task_struct *t, u8 old, u8 new); + +# define rcu_tasks_trace_qs(t) \ + do { \ + if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \ + likely(!READ_ONCE((t)->trc_reader_nesting))) \ + rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \ } while (0) # else # define rcu_tasks_trace_qs(t) do { } while (0) |