From patchwork Wed Sep 13 13:17:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 1833528 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=patchwork.ozlabs.org) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4Rm1Jw3XtDz1yhZ for ; Wed, 13 Sep 2023 23:20:00 +1000 (AEST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qgPl1-00078o-1l; Wed, 13 Sep 2023 09:18:15 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qgPky-00077b-MK; Wed, 13 Sep 2023 09:18:12 -0400 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qgPkv-0002or-LN; Wed, 13 Sep 2023 09:18:12 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 14E482175C; Wed, 13 Sep 2023 16:18:07 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id 0350727C7F; Wed, 13 Sep 2023 16:18:01 +0300 (MSK) Received: (nullmailer pid 4073271 invoked by uid 1000); Wed, 13 Sep 2023 13:18:00 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Alexander Bulekov , Darren Kenny , Thomas Huth , Michael Tokarev Subject: [Stable-8.0.5 02/66] async: Add an optional reentrancy guard to the BH API Date: Wed, 13 Sep 2023 16:17:26 +0300 Message-Id: <20230913131757.4073200-2-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Alexander Bulekov Devices can pass their MemoryReentrancyGuard (from their DeviceState), when creating new BHes. Then, the async API will toggle the guard before/after calling the BH call-back. This prevents bh->mmio reentrancy issues. Signed-off-by: Alexander Bulekov Reviewed-by: Darren Kenny Message-Id: <20230427211013.2994127-3-alxndr@bu.edu> [thuth: Fix "line over 90 characters" checkpatch.pl error] Signed-off-by: Thomas Huth (cherry picked from commit 9c86c97f12c060bf7484dd931f38634e166a81f0) Signed-off-by: Michael Tokarev diff --git a/docs/devel/multiple-iothreads.txt b/docs/devel/multiple-iothreads.txt index 343120f2ef..a3e949f6b3 100644 --- a/docs/devel/multiple-iothreads.txt +++ b/docs/devel/multiple-iothreads.txt @@ -61,6 +61,7 @@ There are several old APIs that use the main loop AioContext: * LEGACY qemu_aio_set_event_notifier() - monitor an event notifier * LEGACY timer_new_ms() - create a timer * LEGACY qemu_bh_new() - create a BH + * LEGACY qemu_bh_new_guarded() - create a BH with a device re-entrancy guard * LEGACY qemu_aio_wait() - run an event loop iteration Since they implicitly work on the main loop they cannot be used in code that @@ -72,8 +73,14 @@ Instead, use the AioContext functions directly (see include/block/aio.h): * aio_set_event_notifier() - monitor an event notifier * aio_timer_new() - create a timer * aio_bh_new() - create a BH + * aio_bh_new_guarded() - create a BH with a device re-entrancy guard * aio_poll() - run an event loop iteration +The qemu_bh_new_guarded/aio_bh_new_guarded APIs accept a "MemReentrancyGuard" +argument, which is used to check for and prevent re-entrancy problems. For +BHs associated with devices, the reentrancy-guard is contained in the +corresponding DeviceState and named "mem_reentrancy_guard". + The AioContext can be obtained from the IOThread using iothread_get_aio_context() or for the main loop using qemu_get_aio_context(). Code that takes an AioContext argument works both in IOThreads or the main diff --git a/include/block/aio.h b/include/block/aio.h index 543717f294..db6f23c619 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -23,6 +23,8 @@ #include "qemu/thread.h" #include "qemu/timer.h" #include "block/graph-lock.h" +#include "hw/qdev-core.h" + typedef struct BlockAIOCB BlockAIOCB; typedef void BlockCompletionFunc(void *opaque, int ret); @@ -331,9 +333,11 @@ void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, * is opaque and must be allocated prior to its use. * * @name: A human-readable identifier for debugging purposes. + * @reentrancy_guard: A guard set when entering a cb to prevent + * device-reentrancy issues */ QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, - const char *name); + const char *name, MemReentrancyGuard *reentrancy_guard); /** * aio_bh_new: Allocate a new bottom half structure @@ -342,7 +346,17 @@ QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, * string. */ #define aio_bh_new(ctx, cb, opaque) \ - aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb))) + aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)), NULL) + +/** + * aio_bh_new_guarded: Allocate a new bottom half structure with a + * reentrancy_guard + * + * A convenience wrapper for aio_bh_new_full() that uses the cb as the name + * string. + */ +#define aio_bh_new_guarded(ctx, cb, opaque, guard) \ + aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)), guard) /** * aio_notify: Force processing of pending events. diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h index b3e54e00bc..68e70e61aa 100644 --- a/include/qemu/main-loop.h +++ b/include/qemu/main-loop.h @@ -387,9 +387,12 @@ void qemu_cond_timedwait_iothread(QemuCond *cond, int ms); /* internal interfaces */ +#define qemu_bh_new_guarded(cb, opaque, guard) \ + qemu_bh_new_full((cb), (opaque), (stringify(cb)), guard) #define qemu_bh_new(cb, opaque) \ - qemu_bh_new_full((cb), (opaque), (stringify(cb))) -QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name); + qemu_bh_new_full((cb), (opaque), (stringify(cb)), NULL) +QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name, + MemReentrancyGuard *reentrancy_guard); void qemu_bh_schedule_idle(QEMUBH *bh); enum { diff --git a/tests/unit/ptimer-test-stubs.c b/tests/unit/ptimer-test-stubs.c index f2bfcede93..8c9407c560 100644 --- a/tests/unit/ptimer-test-stubs.c +++ b/tests/unit/ptimer-test-stubs.c @@ -107,7 +107,8 @@ int64_t qemu_clock_deadline_ns_all(QEMUClockType type, int attr_mask) return deadline; } -QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name) +QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name, + MemReentrancyGuard *reentrancy_guard) { QEMUBH *bh = g_new(QEMUBH, 1); diff --git a/util/async.c b/util/async.c index 856e1a8a33..9df7674b4e 100644 --- a/util/async.c +++ b/util/async.c @@ -65,6 +65,7 @@ struct QEMUBH { void *opaque; QSLIST_ENTRY(QEMUBH) next; unsigned flags; + MemReentrancyGuard *reentrancy_guard; }; /* Called concurrently from any thread */ @@ -137,7 +138,7 @@ void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, } QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, - const char *name) + const char *name, MemReentrancyGuard *reentrancy_guard) { QEMUBH *bh; bh = g_new(QEMUBH, 1); @@ -146,13 +147,28 @@ QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, .cb = cb, .opaque = opaque, .name = name, + .reentrancy_guard = reentrancy_guard, }; return bh; } void aio_bh_call(QEMUBH *bh) { + bool last_engaged_in_io = false; + + if (bh->reentrancy_guard) { + last_engaged_in_io = bh->reentrancy_guard->engaged_in_io; + if (bh->reentrancy_guard->engaged_in_io) { + trace_reentrant_aio(bh->ctx, bh->name); + } + bh->reentrancy_guard->engaged_in_io = true; + } + bh->cb(bh->opaque); + + if (bh->reentrancy_guard) { + bh->reentrancy_guard->engaged_in_io = last_engaged_in_io; + } } /* Multiple occurrences of aio_bh_poll cannot be called concurrently. */ diff --git a/util/main-loop.c b/util/main-loop.c index e180c85145..7022f02ef8 100644 --- a/util/main-loop.c +++ b/util/main-loop.c @@ -605,9 +605,11 @@ void main_loop_wait(int nonblocking) /* Functions to operate on the main QEMU AioContext. */ -QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name) +QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name, + MemReentrancyGuard *reentrancy_guard) { - return aio_bh_new_full(qemu_aio_context, cb, opaque, name); + return aio_bh_new_full(qemu_aio_context, cb, opaque, name, + reentrancy_guard); } /* diff --git a/util/trace-events b/util/trace-events index 16f78d8fe5..3f7e766683 100644 --- a/util/trace-events +++ b/util/trace-events @@ -11,6 +11,7 @@ poll_remove(void *ctx, void *node, int fd) "ctx %p node %p fd %d" # async.c aio_co_schedule(void *ctx, void *co) "ctx %p co %p" aio_co_schedule_bh_cb(void *ctx, void *co) "ctx %p co %p" +reentrant_aio(void *ctx, const char *name) "ctx %p name %s" # thread-pool.c thread_pool_submit(void *pool, void *req, void *opaque) "pool %p req %p opaque %p"