[lustre-devel] lustre: RFC patch to restore watchdog functionality
NeilBrown
neilb at suse.com
Sun Aug 5 20:40:59 PDT 2018
Lustre in drivers/staging lost the watchdog functionality some time ago
Commit: 5d4450c41fe3 ("staging/lustre: fix build error on non-x86 platforms")
This is an attempt to provide the same core functionality in a simpler
way. It compiles, but I haven't tested it.
I don't plan to pursue this further at the moment, but as watchdogs have
been under discussion lately I thought it might be interesting to some.
NeilBrown
From: NeilBrown <neilb at suse.com>
Date: Mon, 6 Aug 2018 13:37:40 +1000
Subject: [PATCH] lustre: add watchdog for ptlrpc service threads.
If a ptlrpc thread takes longer than expected, it
can be used to get a stack trace to see where the
problem is.
This patch restores this functionality by using
a delayed work struct to report a back trace of
the thread if it ever fires.
Signed-off-by: NeilBrown <neilb at suse.com>
---
drivers/staging/lustre/lustre/include/lustre_net.h | 10 +--
drivers/staging/lustre/lustre/ptlrpc/service.c | 87 ++++++++++++++++++----
2 files changed, 76 insertions(+), 21 deletions(-)
diff --git a/drivers/staging/lustre/lustre/include/lustre_net.h b/drivers/staging/lustre/lustre/include/lustre_net.h
index 361b8970368e..3eccec7c7dcc 100644
--- a/drivers/staging/lustre/lustre/include/lustre_net.h
+++ b/drivers/staging/lustre/lustre/include/lustre_net.h
@@ -1283,18 +1283,14 @@ struct ptlrpc_thread {
*/
unsigned int t_id;
/**
- * service thread pid
+ * service thread
*/
+ struct task_struct *t_task;
pid_t t_pid;
/**
* put watchdog in the structure per thread b=14840
- *
- * Lustre watchdog is removed for client in the hope
- * of a generic watchdog can be merged in kernel.
- * When that happens, we should add below back.
- *
- * struct lc_watchdog *t_watchdog;
*/
+ struct delayed_work t_watchdog;
/**
* the svc this thread belonged to b=18582
*/
diff --git a/drivers/staging/lustre/lustre/ptlrpc/service.c b/drivers/staging/lustre/lustre/ptlrpc/service.c
index 55f68b9b3818..4d508a691e89 100644
--- a/drivers/staging/lustre/lustre/ptlrpc/service.c
+++ b/drivers/staging/lustre/lustre/ptlrpc/service.c
@@ -1949,6 +1949,73 @@ ptlrpc_at_check(struct ptlrpc_service_part *svcpt)
return svcpt->scp_at_check;
}
+/*
+ * If a thread spends too long, we want to know about it,
+ * so we set up a delayed work item as a watchdog.
+ * If it fires, we display a stack trace of the delayed thread,
+ * providing we aren't rate-limited
+ */
+#ifdef CONFIG_STACKTRACE
+#define MAX_STACK_TRACE_DEPTH 64
+static void lc_watchdog_fire(struct work_struct *w)
+{
+ struct ptlrpc_thread *thread = container_of(w, struct ptlrpc_thread,
+ t_watchdog.work);
+ struct stack_trace trace;
+ unsigned long *entries;
+ unsigned int i;
+ static DEFINE_RATELIMIT_STATE(_rs,
+ DEFAULT_RATELIMIT_INTERVAL,
+ DEFAULT_RATELIMIT_BURST);
+
+ pr_emerg("ptlrpc thread %d blocked for too long\n", thread->t_pid);
+
+ if (!__ratelimit(&_rs))
+ return;
+
+ entries = kmalloc_array(MAX_STACK_TRACE_DEPTH, sizeof(*entries),
+ GFP_KERNEL);
+ if (!entries)
+ return;
+
+ trace.nr_entries = 0;
+ trace.max_entries = MAX_STACK_TRACE_DEPTH;
+ trace.entries = entries;
+ trace.skip = 0;
+
+ pr_warn("Stack trace of blocked thread\n");
+ save_stack_trace_tsk(thread->t_task, &trace);
+
+ for (i = 0; i < trace.nr_entries; i++)
+ pr_warn("[<0>] %pB\n", (void *)entries[i]);
+
+ kfree(entries);
+}
+#else
+static void lc_watchdog_fire(struct work_struct *w)
+{
+ struct ptlrpc_thread *thread = container_of(w, struct ptlrpc_thread,
+ lc_watchdog.work);
+ pr_emerg("ptlrpc thread %d blocked for too long\n", thread->t_pid);
+
+}
+#endif
+
+static inline void lc_watchdog_init(struct delayed_work *work, int time)
+{
+ INIT_DELAYED_WORK(work, lc_watchdog_fire);
+ schedule_delayed_work(work, time);
+}
+
+static inline void lc_watchdog_disable(struct delayed_work *work)
+{
+ cancel_delayed_work_sync(work);
+}
+static inline void lc_watchdog_touch(struct delayed_work *work, int time)
+{
+ mod_delayed_work(system_wq, work, time);
+}
+
/**
* requests wait on preprocessing
* user can call it w/o any lock but need to hold
@@ -1972,9 +2039,7 @@ ptlrpc_wait_event(struct ptlrpc_service_part *svcpt,
{
/* Don't exit while there are replies to be handled */
- /* XXX: Add this back when libcfs watchdog is merged upstream
- lc_watchdog_disable(thread->t_watchdog);
- */
+ lc_watchdog_disable(&thread->t_watchdog);
cond_resched();
@@ -2001,10 +2066,8 @@ ptlrpc_wait_event(struct ptlrpc_service_part *svcpt,
if (ptlrpc_thread_stopping(thread))
return -EINTR;
- /*
- lc_watchdog_touch(thread->t_watchdog,
+ lc_watchdog_touch(&thread->t_watchdog,
ptlrpc_server_get_timeout(svcpt));
- */
return 0;
}
@@ -2024,6 +2087,7 @@ static int ptlrpc_main(void *arg)
struct lu_env *env;
int counter = 0, rc = 0;
+ thread->t_task = current;
thread->t_pid = current->pid;
unshare_fs_struct();
@@ -2104,10 +2168,8 @@ static int ptlrpc_main(void *arg)
/* wake up our creator in case he's still waiting. */
wake_up(&thread->t_ctl_waitq);
- /*
- thread->t_watchdog = lc_watchdog_add(ptlrpc_server_get_timeout(svcpt),
- NULL, NULL);
- */
+ lc_watchdog_init(&thread->t_watchdog,
+ ptlrpc_server_get_timeout(svcpt));
spin_lock(&svcpt->scp_rep_lock);
list_add(&rs->rs_list, &svcpt->scp_rep_idle);
@@ -2163,10 +2225,7 @@ static int ptlrpc_main(void *arg)
}
}
- /*
- lc_watchdog_delete(thread->t_watchdog);
- thread->t_watchdog = NULL;
- */
+ lc_watchdog_disable(&thread->t_watchdog);
out_srv_fini:
/*
--
2.14.0.rc0.dirty
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