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rcu-tasks: Track blocked RCU Tasks Trace readers

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This commit places any task that has ever blocked within its current
RCU Tasks Trace read-side critical section on a per-CPU list within the
rcu_tasks_percpu structure.  Tasks are removed from this list when they
exit by the exit_tasks_rcu_finish_trace() function.  The purpose of this
commit is to provide the information needed to eliminate the current
scan of the full task list.

This commit offsets the INT_MIN value for ->trc_reader_nesting with the
new nesting level in order to avoid queueing tasks that are exiting
their read-side critical sections.

[ paulmck: Apply kernel test robot feedback. ]
[ paulmck: Apply feedback from syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: syzbot <syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com>
Tested-by: "Zhang, Qiang1" <qiang1.zhang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.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>
This commit is contained in:
Paul E. McKenney
2022-05-17 11:30:32 -07:00
parent 434c9eefb9
commit 0356d4e662
3 changed files with 31 additions and 4 deletions
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11
include/linux/rcupdate.h
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@@ -174,12 +174,19 @@ void synchronize_rcu_tasks(void);
#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);
void rcu_tasks_trace_qs_blkd(struct task_struct *t);
# define rcu_tasks_trace_qs(t) \
do { \
int ___rttq_nesting = READ_ONCE((t)->trc_reader_nesting); \
\
if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \
likely(!READ_ONCE((t)->trc_reader_nesting))) \
likely(!___rttq_nesting)) { \
rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \
} else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \
!READ_ONCE((t)->trc_reader_special.b.blocked)) { \
rcu_tasks_trace_qs_blkd(t); \
} \
} while (0)
# else
# define rcu_tasks_trace_qs(t) do { } while (0)
@@ -188,7 +195,7 @@ u8 rcu_trc_cmpxchg_need_qs(struct task_struct *t, u8 old, u8 new);
#define rcu_tasks_qs(t, preempt) \
do { \
rcu_tasks_classic_qs((t), (preempt)); \
rcu_tasks_trace_qs((t)); \
rcu_tasks_trace_qs(t); \
} while (0)
# ifdef CONFIG_TASKS_RUDE_RCU