path: root/kernel/rcutree_trace.c
diff options
authorPaul E. McKenney <paul.mckenney@linaro.org>2012-01-30 17:02:47 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-02-21 09:06:07 -0800
commit2036d94a7b61ca5032ce90f2bda06afec0fe713e (patch)
treefc9f4b5ba1058e5a2fdf9ccd187766c90f5ae036 /kernel/rcutree_trace.c
parentc5fdcec927ee31fc96e92339c3a83ac6e0725289 (diff)
rcu: Rework detection of use of RCU by offline CPUs
Because newly offlined CPUs continue executing after completing the CPU_DYING notifiers, they legitimately enter the scheduler and use RCU while appearing to be offline. This calls for a more sophisticated approach as follows: 1. RCU marks the CPU online during the CPU_UP_PREPARE phase. 2. RCU marks the CPU offline during the CPU_DEAD phase. 3. Diagnostics regarding use of read-side RCU by offline CPUs use RCU's accounting rather than the cpu_online_map. (Note that __call_rcu() still uses cpu_online_map to detect illegal invocations within CPU_DYING notifiers.) 4. Offline CPUs are prevented from hanging the system by force_quiescent_state(), which pays attention to cpu_online_map. Some additional work (in a later commit) will be needed to guarantee that force_quiescent_state() waits a full jiffy before assuming that a CPU is offline, for example, when called from idle entry. (This commit also makes the one-jiffy wait explicit, since the old-style implicit wait can now be defeated by RCU_FAST_NO_HZ and by rcutorture.) This approach avoids the false positives encountered when attempting to use more exact classification of CPU online/offline state. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree_trace.c')
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index db0987c1e1b..ed459edeff4 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -72,7 +72,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
- seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi);
+ seq_printf(m, " of=%lu", rdp->offline_fqs);
seq_printf(m, " ql=%ld/%ld qs=%c%c%c%c",
rdp->qlen_lazy, rdp->qlen,
".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
@@ -144,7 +144,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
- seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi);
+ seq_printf(m, ",%lu", rdp->offline_fqs);
seq_printf(m, ",%ld,%ld,\"%c%c%c%c\"", rdp->qlen_lazy, rdp->qlen,
".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
@@ -168,7 +168,7 @@ static int show_rcudata_csv(struct seq_file *m, void *unused)
seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pgp\",\"pq\",");
seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\",");
- seq_puts(m, "\"of\",\"ri\",\"qll\",\"ql\",\"qs\"");
+ seq_puts(m, "\"of\",\"qll\",\"ql\",\"qs\"");
seq_puts(m, "\"kt\",\"ktl\"");
#endif /* #ifdef CONFIG_RCU_BOOST */