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Date:   Wed, 18 Nov 2020 07:39:08 -0800
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Subject: [RFC PATCH v3 22/61] e2fsck: add debug codes for multiple threads
From:   Saranya Muruganandam <saranyamohan@google.com>
To:     linux-ext4@vger.kernel.org, tytso@mit.edu
Cc:     adilger.kernel@dilger.ca, Li Xi <lixi@ddn.com>,
        Wang Shilong <wshilong@ddn.com>,
        Saranya Muruganandam <saranyamohan@google.com>
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From: Li Xi <lixi@ddn.com>

These debug codes are added to run the multiple pass1 check
thread one by one in order. If all the codes are correct,
fsck of multiple threads should have exactly the same outcome
with single thread.

Signed-off-by: Li Xi <lixi@ddn.com>
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Signed-off-by: Saranya Muruganandam <saranyamohan@google.com>
---
 e2fsck/e2fsck.h | 16 ++++++++++++++++
 e2fsck/pass1.c  | 29 +++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/e2fsck/e2fsck.h b/e2fsck/e2fsck.h
index 6783ed05..972c8410 100644
--- a/e2fsck/e2fsck.h
+++ b/e2fsck/e2fsck.h
@@ -450,6 +450,18 @@ struct e2fsck_struct {
 };
 
 #ifdef CONFIG_PFSCK
+#ifdef DEBUG_THREADS
+/*
+ * Enabling DEBUG_THREADS would cause the parallel
+ * fsck threads run sequentially.
+ */
+struct e2fsck_thread_debug {
+	pthread_mutex_t	etd_mutex;
+	pthread_cond_t	etd_cond;
+	int		etd_finished_threads;
+};
+#endif
+
 struct e2fsck_thread_info {
 	/* ID returned by pthread_create() */
 	pthread_t		 eti_thread_id;
@@ -459,7 +471,11 @@ struct e2fsck_thread_info {
 	int			 eti_started;
 	/* Context used for this thread */
 	e2fsck_t		 eti_thread_ctx;
+#ifdef DEBUG_THREADS
+	struct e2fsck_thread_debug	*eti_debug;
+#endif
 };
+
 #endif
 
 /* Data structures to evaluate whether an extent tree needs rebuilding. */
diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index 75298d9d..f36b3e70 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -2641,6 +2641,18 @@ static void *e2fsck_pass1_thread(void *arg)
 {
 	struct e2fsck_thread_info	*info = arg;
 	e2fsck_t			 thread_ctx = info->eti_thread_ctx;
+#ifdef DEBUG_THREADS
+	struct e2fsck_thread_debug	*thread_debug = info->eti_debug;
+#endif
+
+#ifdef DEBUG_THREADS
+	pthread_mutex_lock(&thread_debug->etd_mutex);
+	while (info->eti_thread_index > thread_debug->etd_finished_threads) {
+		pthread_cond_wait(&thread_debug->etd_cond,
+				  &thread_debug->etd_mutex);
+	}
+	pthread_mutex_unlock(&thread_debug->etd_mutex);
+#endif
 
 #ifdef HAVE_SETJMP_H
 	/*
@@ -2665,6 +2677,14 @@ out:
 			thread_ctx->thread_info.et_group_start,
 			thread_ctx->thread_info.et_group_end,
 			thread_ctx->thread_info.et_inode_number);
+
+#ifdef DEBUG_THREADS
+	pthread_mutex_lock(&thread_debug->etd_mutex);
+	thread_debug->etd_finished_threads++;
+	pthread_cond_broadcast(&thread_debug->etd_cond);
+	pthread_mutex_unlock(&thread_debug->etd_mutex);
+#endif
+
 	return NULL;
 }
 
@@ -2678,6 +2698,12 @@ static int e2fsck_pass1_threads_start(struct e2fsck_thread_info **pinfo,
 	struct e2fsck_thread_info	*tmp_pinfo;
 	int				 i;
 	e2fsck_t			 thread_ctx;
+#ifdef DEBUG_THREADS
+	struct e2fsck_thread_debug	 thread_debug =
+		{PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, 0};
+
+	thread_debug.etd_finished_threads = 0;
+#endif
 
 	retval = pthread_attr_init(&attr);
 	if (retval) {
@@ -2698,6 +2724,9 @@ static int e2fsck_pass1_threads_start(struct e2fsck_thread_info **pinfo,
 	for (i = 0; i < num_threads; i++) {
 		tmp_pinfo = &infos[i];
 		tmp_pinfo->eti_thread_index = i;
+#ifdef DEBUG_THREADS
+		tmp_pinfo->eti_debug = &thread_debug;
+#endif
 		retval = e2fsck_pass1_thread_prepare(global_ctx, &thread_ctx,
 						     i, num_threads);
 		if (retval) {
-- 
2.29.2.299.gdc1121823c-goog