From: Yordan Karadzhov <ykaradzhov@vmware.com>
To: "rostedt@goodmis.org" <rostedt@goodmis.org>
Cc: "linux-trace-devel@vger.kernel.org" <linux-trace-devel@vger.kernel.org>
Subject: [PATCH 1/2] kernel-shark-qt: Avoid race condition when reading data
Date: Fri, 4 Jan 2019 20:06:20 +0000 [thread overview]
Message-ID: <20190104200559.24471-2-ykaradzhov@vmware.com> (raw)
In-Reply-To: <20190104200559.24471-1-ykaradzhov@vmware.com>
We know that the data reading operations are not thread-safe.
A permanent solution for the problem is being worked on. For
the time being, this patch provides a naive temporary fix by
slapping mutexes all over the code, which will slow things down
a bit.
Signed-off-by: Yordan Karadzhov <ykaradzhov@vmware.com>
---
kernel-shark-qt/src/libkshark.c | 74 +++++++++++++---------
kernel-shark-qt/src/libkshark.h | 3 -
kernel-shark-qt/src/plugins/sched_events.c | 6 +-
3 files changed, 47 insertions(+), 36 deletions(-)
diff --git a/kernel-shark-qt/src/libkshark.c b/kernel-shark-qt/src/libkshark.c
index 598ea52..23dc813 100644
--- a/kernel-shark-qt/src/libkshark.c
+++ b/kernel-shark-qt/src/libkshark.c
@@ -960,31 +960,6 @@ ssize_t kshark_load_data_records(struct kshark_context *kshark_ctx,
return -ENOMEM;
}
-/**
- * @brief A thread-safe read of a record from a specific offset.
- *
- * @param kshark_ctx: Input location for the session context pointer.
- * @param offset: the offset into the file to find the record.
- *
- * @returns The returned pevent_record must be freed.
- */
-struct tep_record *kshark_read_at(struct kshark_context *kshark_ctx,
- uint64_t offset)
-{
- /*
- * Calling tracecmd_read_at() is not thread-safe. Use a mutex to
- * protect the access.
- */
- pthread_mutex_lock(&kshark_ctx->input_mutex);
-
- struct tep_record *data = tracecmd_read_at(kshark_ctx->handle,
- offset, NULL);
-
- pthread_mutex_unlock(&kshark_ctx->input_mutex);
-
- return data;
-}
-
static const char *kshark_get_latency(struct tep_handle *pe,
struct tep_record *record)
{
@@ -1046,10 +1021,18 @@ int kshark_get_pid_easy(struct kshark_entry *entry)
/*
* The entry has been touched by a plugin callback function.
* Because of this we do not trust the value of "entry->pid".
+ *
+ * Currently the data reading operations are not thread-safe.
+ * Use a mutex to protect the access.
*/
- data = kshark_read_at(kshark_ctx, entry->offset);
+ pthread_mutex_lock(&kshark_ctx->input_mutex);
+
+ data = tracecmd_read_at(kshark_ctx->handle, entry->offset,
+ NULL);
pid = tep_data_pid(kshark_ctx->pevent, data);
free_record(data);
+
+ pthread_mutex_unlock(&kshark_ctx->input_mutex);
}
return pid;
@@ -1106,10 +1089,18 @@ const char *kshark_get_latency_easy(struct kshark_entry *entry)
if (entry->event_id < 0)
return NULL;
- data = kshark_read_at(kshark_ctx, entry->offset);
+ /*
+ * Currently the data reading operations are not thread-safe.
+ * Use a mutex to protect the access.
+ */
+ pthread_mutex_lock(&kshark_ctx->input_mutex);
+
+ data = tracecmd_read_at(kshark_ctx->handle, entry->offset, NULL);
lat = kshark_get_latency(kshark_ctx->pevent, data);
free_record(data);
+ pthread_mutex_unlock(&kshark_ctx->input_mutex);
+
return lat;
}
@@ -1142,10 +1133,18 @@ int kshark_get_event_id_easy(struct kshark_entry *entry)
* The entry has been touched by a plugin callback function.
* Because of this we do not trust the value of
* "entry->event_id".
+ *
+ * Currently the data reading operations are not thread-safe.
+ * Use a mutex to protect the access.
*/
- data = kshark_read_at(kshark_ctx, entry->offset);
+ pthread_mutex_lock(&kshark_ctx->input_mutex);
+
+ data = tracecmd_read_at(kshark_ctx->handle, entry->offset,
+ NULL);
event_id = tep_data_type(kshark_ctx->pevent, data);
free_record(data);
+
+ pthread_mutex_unlock(&kshark_ctx->input_mutex);
}
return (event_id == -1)? -EFAULT : event_id;
@@ -1184,7 +1183,14 @@ const char *kshark_get_event_name_easy(struct kshark_entry *entry)
}
}
+ /*
+ * Currently the data reading operations are not thread-safe.
+ * Use a mutex to protect the access.
+ */
+ pthread_mutex_lock(&kshark_ctx->input_mutex);
event = tep_data_event_from_type(kshark_ctx->pevent, event_id);
+ pthread_mutex_unlock(&kshark_ctx->input_mutex);
+
if (event)
return event->name;
@@ -1223,8 +1229,13 @@ const char *kshark_get_info_easy(struct kshark_entry *entry)
}
}
- data = kshark_read_at(kshark_ctx, entry->offset);
+ /*
+ * Currently the data reading operations are not thread-safe.
+ * Use a mutex to protect the access.
+ */
+ pthread_mutex_lock(&kshark_ctx->input_mutex);
+ data = tracecmd_read_at(kshark_ctx->handle, entry->offset, NULL);
event_id = tep_data_type(kshark_ctx->pevent, data);
event = tep_data_event_from_type(kshark_ctx->pevent, event_id);
if (event)
@@ -1232,6 +1243,8 @@ const char *kshark_get_info_easy(struct kshark_entry *entry)
free_record(data);
+ pthread_mutex_unlock(&kshark_ctx->input_mutex);
+
return info;
}
@@ -1315,7 +1328,8 @@ char* kshark_dump_entry(const struct kshark_entry *entry)
struct tep_event_format *event;
struct tep_record *data;
- data = kshark_read_at(kshark_ctx, entry->offset);
+ data = tracecmd_read_at(kshark_ctx->handle, entry->offset,
+ NULL);
event = tep_data_event_from_type(kshark_ctx->pevent,
entry->event_id);
diff --git a/kernel-shark-qt/src/libkshark.h b/kernel-shark-qt/src/libkshark.h
index 7d1edfc..a1b1f91 100644
--- a/kernel-shark-qt/src/libkshark.h
+++ b/kernel-shark-qt/src/libkshark.h
@@ -183,9 +183,6 @@ char* kshark_dump_custom_entry(struct kshark_context *kshark_ctx,
const struct kshark_entry *entry,
kshark_custom_info_func info_func);
-struct tep_record *kshark_read_at(struct kshark_context *kshark_ctx,
- uint64_t offset);
-
/** Bit masks used to control the visibility of the entry after filtering. */
enum kshark_filter_masks {
/**
diff --git a/kernel-shark-qt/src/plugins/sched_events.c b/kernel-shark-qt/src/plugins/sched_events.c
index 1500110..5409bc6 100644
--- a/kernel-shark-qt/src/plugins/sched_events.c
+++ b/kernel-shark-qt/src/plugins/sched_events.c
@@ -184,7 +184,7 @@ bool plugin_wakeup_match_rec_pid(struct kshark_context *kshark_ctx,
if (plugin_ctx->sched_wakeup_event &&
e->event_id == plugin_ctx->sched_wakeup_event->id) {
- record = kshark_read_at(kshark_ctx, e->offset);
+ record = tracecmd_read_at(kshark_ctx->handle, e->offset, NULL);
/* We only want those that actually woke up the task. */
ret = tep_read_number_field(plugin_ctx->sched_wakeup_success_field,
@@ -196,7 +196,7 @@ bool plugin_wakeup_match_rec_pid(struct kshark_context *kshark_ctx,
if (plugin_ctx->sched_wakeup_new_event &&
e->event_id == plugin_ctx->sched_wakeup_new_event->id) {
- record = kshark_read_at(kshark_ctx, e->offset);
+ record = tracecmd_read_at(kshark_ctx->handle, e->offset, NULL);
/* We only want those that actually woke up the task. */
ret = tep_read_number_field(plugin_ctx->sched_wakeup_new_success_field,
@@ -238,7 +238,7 @@ bool plugin_switch_match_rec_pid(struct kshark_context *kshark_ctx,
e->event_id == plugin_ctx->sched_switch_event->id) {
struct tep_record *record;
- record = kshark_read_at(kshark_ctx, e->offset);
+ record = tracecmd_read_at(kshark_ctx->handle, e->offset, NULL);
ret = tep_read_number_field(plugin_ctx->sched_switch_prev_state_field,
record->data, &val);
--
2.17.1
next prev parent reply other threads:[~2019-01-04 20:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-04 20:06 [PATCH 0/2] Improve/debug the searching logic Yordan Karadzhov
2019-01-04 20:06 ` Yordan Karadzhov [this message]
2019-01-04 20:06 ` [PATCH 2/2] kernel-shark-qt: Implement State machine for searching in the data Yordan Karadzhov
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