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| author | Paul E. McKenney <paulmck@kernel.org> | 2020-01-21 21:30:22 +0100 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-02-21 00:58:23 +0100 |
| commit | 5648d6591230c811972543ff146ce969babdd732 (patch) | |
| tree | b7dadb46a61e606238af01c10f634885cbbc087b /kernel/rcu/tree_stall.h | |
| parent | rculist: Add brackets around cond argument in __list_check_rcu macro (diff) | |
| download | linux-5648d6591230c811972543ff146ce969babdd732.tar.xz linux-5648d6591230c811972543ff146ce969babdd732.zip | |
rcu: Don't flag non-starting GPs before GP kthread is running
Currently rcu_check_gp_start_stall() complains if a grace period takes
too long to start, where "too long" is roughly one RCU CPU stall-warning
interval. This has worked well, but there are some debugging Kconfig
options (such as CONFIG_EFI_PGT_DUMP=y) that can make booting take a
very long time, so much so that the stall-warning interval has expired
before RCU's grace-period kthread has even been spawned.
This commit therefore resets the rcu_state.gp_req_activity and
rcu_state.gp_activity timestamps just before the grace-period kthread
is spawned, and modifies the checks and adds ordering to ensure that
if rcu_check_gp_start_stall() sees that the grace-period kthread
has been spawned, that it will also see the resets applied to the
rcu_state.gp_req_activity and rcu_state.gp_activity timestamps.
Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[ paulmck: Fix whitespace issues reported by Qian Cai. ]
Tested-by: Qian Cai <cai@lca.pw>
[ paulmck: Simplify grace-period wakeup check per Steve Rostedt feedback. ]
Diffstat (limited to 'kernel/rcu/tree_stall.h')
| -rw-r--r-- | kernel/rcu/tree_stall.h | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 488b71d03030..16ad7ad9a185 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -578,6 +578,7 @@ void show_rcu_gp_kthreads(void) unsigned long jw; struct rcu_data *rdp; struct rcu_node *rnp; + struct task_struct *t = READ_ONCE(rcu_state.gp_kthread); j = jiffies; ja = j - READ_ONCE(rcu_state.gp_activity); @@ -585,8 +586,7 @@ void show_rcu_gp_kthreads(void) jw = j - READ_ONCE(rcu_state.gp_wake_time); pr_info("%s: wait state: %s(%d) ->state: %#lx delta ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_flags %#x\n", rcu_state.name, gp_state_getname(rcu_state.gp_state), - rcu_state.gp_state, - rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL, + rcu_state.gp_state, t ? t->state : 0x1ffffL, ja, jr, jw, (long)READ_ONCE(rcu_state.gp_wake_seq), (long)READ_ONCE(rcu_state.gp_seq), (long)READ_ONCE(rcu_get_root()->gp_seq_needed), @@ -633,7 +633,8 @@ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress() || ULONG_CMP_GE(READ_ONCE(rnp_root->gp_seq), - READ_ONCE(rnp_root->gp_seq_needed))) + READ_ONCE(rnp_root->gp_seq_needed)) || + !smp_load_acquire(&rcu_state.gp_kthread)) // Get stable kthread. return; j = jiffies; /* Expensive access, and in common case don't get here. */ if (time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) || |