[RFC PATCH 2/6] job: _locked functions and public job_lock/unlock for next patch

[Emanuele Giuseppe Esposito]

Create _locked functions, to make next patch a little bit smaller.
Also set the locking functions as public, so that they can be used
also from structures using the Job struct.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 include/qemu/job.h | 23 +++++++++++++
 job.c              | 85 ++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 93 insertions(+), 15 deletions(-)

diff --git a/include/qemu/job.h b/include/qemu/job.h
index 72c7d0f69d..ba2f9b2660 100644
--- a/include/qemu/job.h
+++ b/include/qemu/job.h
@@ -305,6 +305,7 @@ void job_txn_add_job(JobTxn *txn, Job *job);
 
 /** Returns the @ret field of a given Job. */
 int job_get_ret(Job *job);
+int job_get_ret_locked(Job *job);
 
 /** Returns the AioContext of a given Job. */
 AioContext *job_get_aiocontext(Job *job);
@@ -336,6 +337,24 @@ bool job_is_force_cancel(Job *job);
 /** Returns the statis of a given Job. */
 JobStatus job_get_status(Job *job);
 
+/**
+ * job_lock:
+ *
+ * Take the mutex protecting the list of jobs and their status.
+ * Most functions called by the monitor need to call job_lock
+ * and job_unlock manually.  On the other hand, function called
+ * by the block jobs themselves and by the block layer will take the
+ * lock for you.
+ */
+void job_lock(void);
+
+/**
+ * job_unlock:
+ *
+ * Release the mutex protecting the list of jobs and their status.
+ */
+void job_unlock(void);
+
 /**
  * Create a new long-running job and return it.
  *
@@ -424,6 +443,7 @@ void job_start(Job *job);
  * Continue the specified job by entering the coroutine.
  */
 void job_enter(Job *job);
+void job_enter_locked(Job *job);
 
 /**
  * @job: The job that is ready to pause.
@@ -462,12 +482,15 @@ bool job_is_internal(Job *job);
 
 /** Returns whether the job is scheduled for cancellation. */
 bool job_is_cancelled(Job *job);
+bool job_is_cancelled_locked(Job *job);
 
 /** Returns whether the job is in a completed state. */
 bool job_is_completed(Job *job);
+bool job_is_completed_locked(Job *job);
 
 /** Returns whether the job is ready to be completed. */
 bool job_is_ready(Job *job);
+bool job_is_ready_locked(Job *job);
 
 /**
  * Request @job to pause at the next pause point. Must be paired with
diff --git a/job.c b/job.c
index 872bbebb01..96fb8e9730 100644
--- a/job.c
+++ b/job.c
@@ -32,6 +32,10 @@
 #include "trace/trace-root.h"
 #include "qapi/qapi-events-job.h"
 
+/* job_mutex protexts the jobs list, but also the job operations. */
+static QemuMutex job_mutex;
+
+/* Protected by job_mutex */
 static QLIST_HEAD(, Job) jobs = QLIST_HEAD_INITIALIZER(jobs);
 
 /* Job State Transition Table */
@@ -64,27 +68,22 @@ bool JobVerbTable[JOB_VERB__MAX][JOB_STATUS__MAX] = {
 /* Transactional group of jobs */
 struct JobTxn {
 
-    /* Is this txn being cancelled? */
+    /* Is this txn being cancelled? Atomic.*/
     bool aborting;
 
-    /* List of jobs */
+    /* List of jobs. Protected by job_mutex. */
     QLIST_HEAD(, Job) jobs;
 
-    /* Reference count */
+    /* Reference count. Atomic. */
     int refcnt;
 };
 
-/* Right now, this mutex is only needed to synchronize accesses to job->busy
- * and job->sleep_timer, such as concurrent calls to job_do_yield and
- * job_enter. */
-static QemuMutex job_mutex;
-
-static void job_lock(void)
+void job_lock(void)
 {
     qemu_mutex_lock(&job_mutex);
 }
 
-static void job_unlock(void)
+void job_unlock(void)
 {
     qemu_mutex_unlock(&job_mutex);
 }
@@ -109,11 +108,22 @@ bool job_is_busy(Job *job)
     return qatomic_read(&job->busy);
 }
 
-int job_get_ret(Job *job)
+/* Called with job_mutex held. */
+int job_get_ret_locked(Job *job)
 {
     return job->ret;
 }
 
+/* Called with job_mutex *not* held. */
+int job_get_ret(Job *job)
+{
+    int ret;
+    job_lock();
+    ret = job_get_ret_locked(job);
+    job_unlock();
+    return ret;
+}
+
 Error *job_get_err(Job *job)
 {
     return job->err;
@@ -255,12 +265,24 @@ const char *job_type_str(const Job *job)
     return JobType_str(job_type(job));
 }
 
-bool job_is_cancelled(Job *job)
+/* Called with job_mutex held. */
+bool job_is_cancelled_locked(Job *job)
 {
     return job->cancelled;
 }
 
-bool job_is_ready(Job *job)
+/* Called with job_mutex *not* held. */
+bool job_is_cancelled(Job *job)
+{
+    bool ret;
+    job_lock();
+    ret = job_is_cancelled_locked(job);
+    job_unlock();
+    return ret;
+}
+
+/* Called with job_mutex held. */
+bool job_is_ready_locked(Job *job)
 {
     switch (job->status) {
     case JOB_STATUS_UNDEFINED:
@@ -282,7 +304,18 @@ bool job_is_ready(Job *job)
     return false;
 }
 
-bool job_is_completed(Job *job)
+/* Called with job_mutex *not* held. */
+bool job_is_ready(Job *job)
+{
+    bool ret;
+    job_lock();
+    ret = job_is_ready_locked(job);
+    job_unlock();
+    return ret;
+}
+
+/* Called with job_mutex held. */
+bool job_is_completed_locked(Job *job)
 {
     switch (job->status) {
     case JOB_STATUS_UNDEFINED:
@@ -304,6 +337,17 @@ bool job_is_completed(Job *job)
     return false;
 }
 
+/* Called with job_mutex *not* held. */
+bool job_is_completed(Job *job)
+{
+    bool ret;
+    job_lock();
+    ret = job_is_completed_locked(job);
+    job_unlock();
+    return ret;
+}
+
+/* Does not need job_mutex. Value is never modified */
 static bool job_started(Job *job)
 {
     return job->co;
@@ -503,11 +547,20 @@ void job_enter_cond(Job *job, bool(*fn)(Job *job))
     aio_co_enter(job->aio_context, job->co);
 }
 
-void job_enter(Job *job)
+/* Called with job_mutex held. */
+void job_enter_locked(Job *job)
 {
     job_enter_cond(job, NULL);
 }
 
+/* Called with job_mutex *not* held. */
+void job_enter(Job *job)
+{
+    job_lock();
+    job_enter_locked(job, NULL);
+    job_unlock();
+}
+
 /* Yield, and schedule a timer to reenter the coroutine after @ns nanoseconds.
  * Reentering the job coroutine with job_enter() before the timer has expired
  * is allowed and cancels the timer.
@@ -684,12 +737,14 @@ void job_dismiss(Job **jobptr, Error **errp)
     *jobptr = NULL;
 }
 
+/* Called with job_mutex held. */
 void job_early_fail(Job *job)
 {
     assert(job->status == JOB_STATUS_CREATED);
     job_do_dismiss(job);
 }
 
+/* Called with job_mutex held. */
 static void job_conclude(Job *job)
 {
     job_state_transition(job, JOB_STATUS_CONCLUDED);
-- 
2.31.1