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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2009-09-13 18:15:09 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-09-18 00:06:13 +0200 |
| commit | b0e165c035b13e1074fa0b555318bd9cb7102558 (patch) | |
| tree | c65de438df4e8ad3e9e562663b377d61cc87af57 /kernel/rcutree_plugin.h | |
| parent | rcu: Kconfig help needs to say that TREE_PREEMPT_RCU scales down (diff) | |
| download | linux-b0e165c035b13e1074fa0b555318bd9cb7102558.tar.xz linux-b0e165c035b13e1074fa0b555318bd9cb7102558.zip | |
rcu: Add debug checks to TREE_PREEMPT_RCU for premature grace periods
Check to make sure that there are no blocked tasks for the previous
grace period while initializing for the next grace period, verify
that rcu_preempt_qs() is given the correct CPU number and is never
called for an offline CPU.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
LKML-Reference: <12528585111986-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree_plugin.h')
| -rw-r--r-- | kernel/rcutree_plugin.h | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 47789369ea59..b8e4b0384f00 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -86,6 +86,7 @@ static void rcu_preempt_qs(int cpu) if (t->rcu_read_lock_nesting && (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { + WARN_ON_ONCE(cpu != smp_processor_id()); /* Possibly blocking in an RCU read-side critical section. */ rdp = rcu_preempt_state.rda[cpu]; @@ -103,7 +104,11 @@ static void rcu_preempt_qs(int cpu) * state for the current grace period), then as long * as that task remains queued, the current grace period * cannot end. + * + * But first, note that the current CPU must still be + * on line! */ + WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0); phase = !(rnp->qsmask & rdp->grpmask) ^ (rnp->gpnum & 0x1); list_add(&t->rcu_node_entry, &rnp->blocked_tasks[phase]); smp_mb(); /* Ensure later ctxt swtch seen after above. */ @@ -259,6 +264,18 @@ static void rcu_print_task_stall(struct rcu_node *rnp) #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ /* + * Check that the list of blocked tasks for the newly completed grace + * period is in fact empty. It is a serious bug to complete a grace + * period that still has RCU readers blocked! This function must be + * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock + * must be held by the caller. + */ +static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) +{ + WARN_ON_ONCE(!list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1])); +} + +/* * Check for preempted RCU readers for the specified rcu_node structure. * If the caller needs a reliable answer, it must hold the rcu_node's * >lock. @@ -451,6 +468,14 @@ static void rcu_print_task_stall(struct rcu_node *rnp) #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ /* + * Because there is no preemptable RCU, there can be no readers blocked, + * so there is no need to check for blocked tasks. + */ +static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) +{ +} + +/* * Because preemptable RCU does not exist, there are never any preempted * RCU readers. */ |