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| author |   Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2018-05-15 16:23:23 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2018-07-12 15:39:10 -0700 |
| commit | f2e2df59786d7bd52e6e7e2d10c1c6ba433a0ee7 (patch) | |
| tree | 83228ad0b1384cdb37e5be871f21f9d1cbababc8 /kernel/rcu | |
| parent | rcu: Record ->gp_state for both phases of grace-period initialization (diff) | |
| download | linux-dev-f2e2df59786d7bd52e6e7e2d10c1c6ba433a0ee7.tar.xz linux-dev-f2e2df59786d7bd52e6e7e2d10c1c6ba433a0ee7.zip | |
rcu: Add diagnostics for offline CPUs failing to report QS
CPUs are expected to report quiescent states when coming online and
when going offline, and grace-period initialization is supposed to
handle any race conditions where a CPU's ->qsmask bit is set just after
it goes offline. This commit adds diagnostics for the case where an
offline CPU nevertheless has a grace period waiting on it.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 22 | ||||
| -rw-r--r-- | kernel/rcu/tree.h | 1 |
2 files changed, 23 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index ee218d743226..d3333ee2c6f5 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1188,6 +1188,27 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) smp_store_release(ruqp, true); } + /* If waiting too long on an offline CPU, complain. */ + if (!(rdp->grpmask & rcu_rnp_online_cpus(rnp)) && + time_after(jiffies, rdp->rsp->gp_start + HZ)) { + bool onl; + struct rcu_node *rnp1; + + WARN_ON(1); /* Offline CPUs are supposed to report QS! */ + pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n", + __func__, rnp->grplo, rnp->grphi, rnp->level, + (long)rnp->gp_seq, (long)rnp->completedqs); + for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent) + pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx ->rcu_gp_init_mask %#lx\n", + __func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask); + onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp)); + pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n", + __func__, rdp->cpu, ".o"[onl], + (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, + (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); + return 1; /* Break things loose after complaining. */ + } + /* * A CPU running for an extended time within the kernel can * delay RCU grace periods. When the CPU is in NO_HZ_FULL mode, @@ -1967,6 +1988,7 @@ static bool rcu_gp_init(struct rcu_state *rsp) rnp->grphi, rnp->qsmask); /* Quiescent states for tasks on any now-offline CPUs. */ mask = rnp->qsmask & ~rnp->qsmaskinitnext; + rnp->rcu_gp_init_mask = mask; if ((mask || rnp->wait_blkd_tasks) && rcu_is_leaf_node(rnp)) rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags); else diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 8077aff7ab40..d51e6edc8e83 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -90,6 +90,7 @@ struct rcu_node { /* an rcu_data structure, otherwise, each */ /* bit corresponds to a child rcu_node */ /* structure. */ + unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */ unsigned long qsmaskinit; /* Per-GP initial value for qsmask. */ /* Initialized from ->qsmaskinitnext at the */ |