diff options
Diffstat (limited to 'kernel/rcu/tasks.h')
| -rw-r--r-- | kernel/rcu/tasks.h | 36 |
1 files changed, 26 insertions, 10 deletions
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 94b8ee84bc78..28f628c70245 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -951,7 +951,7 @@ reset_ipi: static bool trc_inspect_reader(struct task_struct *t, void *arg) { int cpu = task_cpu(t); - bool in_qs = false; + int nesting; bool ofl = cpu_is_offline(cpu); if (task_curr(t)) { @@ -971,18 +971,18 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg) n_heavy_reader_updates++; if (ofl) n_heavy_reader_ofl_updates++; - in_qs = true; + nesting = 0; } else { // The task is not running, so C-language access is safe. - in_qs = likely(!t->trc_reader_nesting); + nesting = t->trc_reader_nesting; } - // Mark as checked so that the grace-period kthread will - // remove it from the holdout list. - t->trc_reader_checked = true; - - if (in_qs) - return true; // Already in quiescent state, done!!! + // If not exiting a read-side critical section, mark as checked + // so that the grace-period kthread will remove it from the + // holdout list. + t->trc_reader_checked = nesting >= 0; + if (nesting <= 0) + return !nesting; // If in QS, done, otherwise try again later. // The task is in a read-side critical section, so set up its // state so that it will awaken the grace-period kthread upon exit @@ -1041,9 +1041,11 @@ static void trc_wait_for_one_reader(struct task_struct *t, if (smp_call_function_single(cpu, trc_read_check_handler, t, 0)) { // Just in case there is some other reason for // failure than the target CPU being offline. + WARN_ONCE(1, "%s(): smp_call_function_single() failed for CPU: %d\n", + __func__, cpu); rcu_tasks_trace.n_ipis_fails++; per_cpu(trc_ipi_to_cpu, cpu) = false; - t->trc_ipi_to_cpu = cpu; + t->trc_ipi_to_cpu = -1; } } } @@ -1164,14 +1166,28 @@ static void check_all_holdout_tasks_trace(struct list_head *hop, } } +static void rcu_tasks_trace_empty_fn(void *unused) +{ +} + /* Wait for grace period to complete and provide ordering. */ static void rcu_tasks_trace_postgp(struct rcu_tasks *rtp) { + int cpu; bool firstreport; struct task_struct *g, *t; LIST_HEAD(holdouts); long ret; + // Wait for any lingering IPI handlers to complete. Note that + // if a CPU has gone offline or transitioned to userspace in the + // meantime, all IPI handlers should have been drained beforehand. + // Yes, this assumes that CPUs process IPIs in order. If that ever + // changes, there will need to be a recheck and/or timed wait. + for_each_online_cpu(cpu) + if (smp_load_acquire(per_cpu_ptr(&trc_ipi_to_cpu, cpu))) + smp_call_function_single(cpu, rcu_tasks_trace_empty_fn, NULL, 1); + // Remove the safety count. smp_mb__before_atomic(); // Order vs. earlier atomics atomic_dec(&trc_n_readers_need_end); |