From patchwork Fri Jan 4 20:06:20 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yordan Karadzhov X-Patchwork-Id: 10760223 Return-Path: Received: from mail-eopbgr820084.outbound.protection.outlook.com ([40.107.82.84]:56293 "EHLO NAM01-SN1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725930AbfADUIV (ORCPT ); Fri, 4 Jan 2019 15:08:21 -0500 From: Yordan Karadzhov To: "rostedt@goodmis.org" CC: "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 Message-ID: <20190104200559.24471-2-ykaradzhov@vmware.com> References: <20190104200559.24471-1-ykaradzhov@vmware.com> In-Reply-To: <20190104200559.24471-1-ykaradzhov@vmware.com> Content-Language: en-US MIME-Version: 1.0 Sender: linux-trace-devel-owner@vger.kernel.org List-ID: Content-Length: 7285 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 --- 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);