[PATCH] workqueue: add workqueue.mayday_initial_timeout

[ying chen]

If creating a new worker takes longer than MAYDAY_INITIAL_TIMEOUT,
the rescuer thread will be woken up to process works scheduled on
@pool, resulting in sequential execution of all works. This may lead
to a situation where one work blocks others. However, the initial
rescue timeout defaults to 10 milliseconds, which can easily be
triggered in heavy-load environments.
---
 Documentation/admin-guide/kernel-parameters.txt | 4 ++++
 kernel/workqueue.c                              | 5 ++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt
b/Documentation/admin-guide/kernel-parameters.txt
index 149bfa7..be3f488 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -7376,6 +7376,10 @@
                        When enabled, memory and cache locality will be
                        impacted.

+       workqueue.mayday_initial_timeout
+                       Set the initial timeout (jiffies) for the mayday timer.
+                       Default is MAYDAY_INITIAL_TIMEOUT.
+
        writecombine=   [LOONGARCH,EARLY] Control the MAT (Memory Access
                        Type) of ioremap_wc().

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 003474c..c810b61 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -481,6 +481,9 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct
irq_work [NR_STD_WORKER_POOLS],
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
                                     bh_worker_pools);

+static unsigned long wq_mayday_initial_timeout = MAYDAY_INITIAL_TIMEOUT;
+module_param_named(mayday_initial_timeout, wq_mayday_initial_timeout,
ulong, 0644);
+
 /* the per-cpu worker pools */
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
                                     cpu_worker_pools);
@@ -3050,7 +3053,7 @@ static void maybe_create_worker(struct worker_pool *pool)
        raw_spin_unlock_irq(&pool->lock);

        /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
-       mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
+       mod_timer(&pool->mayday_timer, jiffies + wq_mayday_initial_timeout);

        while (true) {
                if (create_worker(pool) || !need_to_create_worker(pool))
--
1.8.3.1