* [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue @ 2018-02-03 15:39 Paolo Bonzini 2018-02-03 15:39 ` [Qemu-devel] [PATCH 1/5] test-coroutine: add simple CoMutex test Paolo Bonzini ` (6 more replies) 0 siblings, 7 replies; 19+ messages in thread From: Paolo Bonzini @ 2018-02-03 15:39 UTC (permalink / raw) To: qemu-devel; +Cc: famz, stefanha, qemu-block There are cases in which a queued coroutine must be restarted from non-coroutine context (with qemu_co_enter_next). In this cases, qemu_co_enter_next also needs to be thread-safe, but it cannot use a CoMutex and so cannot qemu_co_queue_wait. This happens in curl (which right now is rolling its own list of Coroutines) and will happen in Fam's NVMe driver as well. This series extracts the idea of a polymorphic lockable object from my "scoped lock guard" proposal, and applies it to CoQueue. The implementation of QemuLockable is similar to C11 _Generic, but redone using the preprocessor and GCC builtins for compatibility. In general, while a bit on the esoteric side, the functionality used to emulate _Generic is fairly old in GCC, and the builtins are already used by include/qemu/atomic.h; the series was tested with Fedora 27 (boot Damn Small Linux via http) and CentOS 6 (compiled only). Paolo v4->v5: fix checkpatch complaints v3->v4: fix -O0 compilation [Fam] typos and copyright dates [Eric, Fam] improve CoQueue comments [Stefan] Paolo Bonzini (5): test-coroutine: add simple CoMutex test lockable: add QemuLockable coroutine-lock: convert CoQueue to use QemuLockable coroutine-lock: make qemu_co_enter_next thread-safe curl: convert to CoQueue block/curl.c | 20 ++-------- fsdev/qemu-fsdev-throttle.c | 4 +- include/qemu/compiler.h | 40 +++++++++++++++++++ include/qemu/coroutine.h | 29 +++++++++----- include/qemu/lockable.h | 96 +++++++++++++++++++++++++++++++++++++++++++++ include/qemu/thread.h | 5 +-- include/qemu/typedefs.h | 4 ++ tests/test-coroutine.c | 75 ++++++++++++++++++++++++++++++++++- util/qemu-coroutine-lock.c | 22 +++++++---- 9 files changed, 256 insertions(+), 39 deletions(-) create mode 100644 include/qemu/lockable.h -- 2.14.3 ^ permalink raw reply [flat|nested] 19+ messages in thread
* [Qemu-devel] [PATCH 1/5] test-coroutine: add simple CoMutex test 2018-02-03 15:39 [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini @ 2018-02-03 15:39 ` Paolo Bonzini 2018-02-03 20:46 ` Richard Henderson 2018-02-03 15:39 ` [Qemu-devel] [PATCH 2/5] lockable: add QemuLockable Paolo Bonzini ` (5 subsequent siblings) 6 siblings, 1 reply; 19+ messages in thread From: Paolo Bonzini @ 2018-02-03 15:39 UTC (permalink / raw) To: qemu-devel; +Cc: famz, stefanha, qemu-block In preparation for adding a similar test using QemuLockable, add a very simple testcase that has two interleaved calls to lock and unlock. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- tests/test-coroutine.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 48 insertions(+), 2 deletions(-) diff --git a/tests/test-coroutine.c b/tests/test-coroutine.c index 76c646107e..010cb95ad6 100644 --- a/tests/test-coroutine.c +++ b/tests/test-coroutine.c @@ -175,7 +175,7 @@ static void coroutine_fn c1_fn(void *opaque) qemu_coroutine_enter(c2); } -static void test_co_queue(void) +static void test_no_dangling_access(void) { Coroutine *c1; Coroutine *c2; @@ -195,6 +195,51 @@ static void test_co_queue(void) *c1 = tmp; } +static bool locked; +static int done; + +static void coroutine_fn mutex_fn(void *opaque) +{ + CoMutex *m = opaque; + qemu_co_mutex_lock(m); + assert(!locked); + locked = true; + qemu_coroutine_yield(); + locked = false; + qemu_co_mutex_unlock(m); + done++; +} + +static void do_test_co_mutex(CoroutineEntry *entry, void *opaque) +{ + Coroutine *c1 = qemu_coroutine_create(entry, opaque); + Coroutine *c2 = qemu_coroutine_create(entry, opaque); + + done = 0; + qemu_coroutine_enter(c1); + g_assert(locked); + qemu_coroutine_enter(c2); + + /* Unlock queues c2. It is then started automatically when c1 yields or + * terminates. + */ + qemu_coroutine_enter(c1); + g_assert_cmpint(done, ==, 1); + g_assert(locked); + + qemu_coroutine_enter(c2); + g_assert_cmpint(done, ==, 2); + g_assert(!locked); +} + +static void test_co_mutex(void) +{ + CoMutex m; + + qemu_co_mutex_init(&m); + do_test_co_mutex(mutex_fn, &m); +} + /* * Check that creation, enter, and return work */ @@ -422,7 +467,7 @@ int main(int argc, char **argv) * crash, so skip it. */ if (CONFIG_COROUTINE_POOL) { - g_test_add_func("/basic/co_queue", test_co_queue); + g_test_add_func("/basic/no-dangling-access", test_no_dangling_access); } g_test_add_func("/basic/lifecycle", test_lifecycle); @@ -432,6 +477,7 @@ int main(int argc, char **argv) g_test_add_func("/basic/entered", test_entered); g_test_add_func("/basic/in_coroutine", test_in_coroutine); g_test_add_func("/basic/order", test_order); + g_test_add_func("/locking/co-mutex", test_co_mutex); if (g_test_perf()) { g_test_add_func("/perf/lifecycle", perf_lifecycle); g_test_add_func("/perf/nesting", perf_nesting); -- 2.14.3 ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH 1/5] test-coroutine: add simple CoMutex test 2018-02-03 15:39 ` [Qemu-devel] [PATCH 1/5] test-coroutine: add simple CoMutex test Paolo Bonzini @ 2018-02-03 20:46 ` Richard Henderson 0 siblings, 0 replies; 19+ messages in thread From: Richard Henderson @ 2018-02-03 20:46 UTC (permalink / raw) To: Paolo Bonzini, qemu-devel; +Cc: famz, qemu-block, stefanha On 02/03/2018 07:39 AM, Paolo Bonzini wrote: > In preparation for adding a similar test using QemuLockable, add a very > simple testcase that has two interleaved calls to lock and unlock. > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > tests/test-coroutine.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 48 insertions(+), 2 deletions(-) Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~ ^ permalink raw reply [flat|nested] 19+ messages in thread
* [Qemu-devel] [PATCH 2/5] lockable: add QemuLockable 2018-02-03 15:39 [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini 2018-02-03 15:39 ` [Qemu-devel] [PATCH 1/5] test-coroutine: add simple CoMutex test Paolo Bonzini @ 2018-02-03 15:39 ` Paolo Bonzini 2018-02-03 20:44 ` Richard Henderson 2018-02-03 15:39 ` [Qemu-devel] [PATCH 3/5] coroutine-lock: convert CoQueue to use QemuLockable Paolo Bonzini ` (4 subsequent siblings) 6 siblings, 1 reply; 19+ messages in thread From: Paolo Bonzini @ 2018-02-03 15:39 UTC (permalink / raw) To: qemu-devel; +Cc: famz, stefanha, qemu-block QemuLockable is a polymorphic lock type that takes an object and knows which function to use for locking and unlocking. The implementation could use C11 _Generic, but since the support is not very widespread I am instead using __builtin_choose_expr and __builtin_types_compatible_p, which are already used by include/qemu/atomic.h. QemuLockable can be used to implement lock guards, or to pass around a lock in such a way that a function can release it and re-acquire it. The next patch will do this for CoQueue. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- include/qemu/compiler.h | 40 ++++++++++++++++++++ include/qemu/coroutine.h | 4 +- include/qemu/lockable.h | 96 ++++++++++++++++++++++++++++++++++++++++++++++++ include/qemu/thread.h | 5 +-- include/qemu/typedefs.h | 4 ++ tests/test-coroutine.c | 25 +++++++++++++ 6 files changed, 169 insertions(+), 5 deletions(-) create mode 100644 include/qemu/lockable.h diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h index 340e5fdc09..5179bedb1e 100644 --- a/include/qemu/compiler.h +++ b/include/qemu/compiler.h @@ -111,4 +111,44 @@ #define GCC_FMT_ATTR(n, m) #endif +/* Implement C11 _Generic via GCC builtins. Example: + * + * QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x) + * + * The first argument is the discriminator. The last is the default value. + * The middle ones are tuples in "(type, expansion)" format. + */ + +/* First, find out the number of generic cases. */ +#define QEMU_GENERIC(x, ...) \ + QEMU_GENERIC_(typeof(x), __VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) + +/* There will be extra arguments, but they are not used. */ +#define QEMU_GENERIC_(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, count, ...) \ + QEMU_GENERIC##count(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9) + +/* Two more helper macros, this time to extract items from a parenthesized + * list. + */ +#define QEMU_FIRST_(a, b) a +#define QEMU_SECOND_(a, b) b + +/* ... and a final one for the common part of the "recursion". */ +#define QEMU_GENERIC_IF(x, type_then, else_) \ + __builtin_choose_expr(__builtin_types_compatible_p(x, \ + QEMU_FIRST_ type_then), \ + QEMU_SECOND_ type_then, else_) + +/* CPP poor man's "recursion". */ +#define QEMU_GENERIC1(x, a0, ...) (a0) +#define QEMU_GENERIC2(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC1(x, __VA_ARGS__)) +#define QEMU_GENERIC3(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC2(x, __VA_ARGS__)) +#define QEMU_GENERIC4(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC3(x, __VA_ARGS__)) +#define QEMU_GENERIC5(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC4(x, __VA_ARGS__)) +#define QEMU_GENERIC6(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC5(x, __VA_ARGS__)) +#define QEMU_GENERIC7(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC6(x, __VA_ARGS__)) +#define QEMU_GENERIC8(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC7(x, __VA_ARGS__)) +#define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, __VA_ARGS__)) +#define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, __VA_ARGS__)) + #endif /* COMPILER_H */ diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h index ce2eb73670..8a5129741c 100644 --- a/include/qemu/coroutine.h +++ b/include/qemu/coroutine.h @@ -121,7 +121,7 @@ bool qemu_coroutine_entered(Coroutine *co); * Provides a mutex that can be used to synchronise coroutines */ struct CoWaitRecord; -typedef struct CoMutex { +struct CoMutex { /* Count of pending lockers; 0 for a free mutex, 1 for an * uncontended mutex. */ @@ -142,7 +142,7 @@ typedef struct CoMutex { unsigned handoff, sequence; Coroutine *holder; -} CoMutex; +}; /** * Initialises a CoMutex. This must be called before any other operation is used diff --git a/include/qemu/lockable.h b/include/qemu/lockable.h new file mode 100644 index 0000000000..826ac3f675 --- /dev/null +++ b/include/qemu/lockable.h @@ -0,0 +1,96 @@ +/* + * Polymorphic locking functions (aka poor man templates) + * + * Copyright Red Hat, Inc. 2017, 2018 + * + * Author: Paolo Bonzini <pbonzini@redhat.com> + * + * This work is licensed under the terms of the GNU LGPL, version 2 or later. + * See the COPYING.LIB file in the top-level directory. + * + */ + +#ifndef QEMU_LOCKABLE_H +#define QEMU_LOCKABLE_H + +#include "qemu/coroutine.h" +#include "qemu/thread.h" + +typedef void QemuLockUnlockFunc(void *); + +struct QemuLockable { + void *object; + QemuLockUnlockFunc *lock; + QemuLockUnlockFunc *unlock; +}; + +/* This function gives an error if an invalid, non-NULL pointer type is passed + * to QEMU_MAKE_LOCKABLE. For optimized builds, we can rely on dead-code elimination + * from the compiler, and give the errors already at link time. + */ +#ifdef __OPTIMIZE__ +void unknown_lock_type(void *); +#else +static inline void unknown_lock_type(void *unused) +{ + abort(); +} +#endif + +static inline __attribute__((__always_inline__)) QemuLockable * +qemu_make_lockable(void *x, QemuLockable *lockable) +{ + /* We cannot test this in a macro, otherwise we get compiler + * warnings like "the address of 'm' will always evaluate as 'true'". + */ + return x ? lockable : NULL; +} + +/* Auxiliary macros to simplify QEMU_MAKE_LOCABLE. */ +#define QEMU_LOCK_FUNC(x) ((QemuLockUnlockFunc *) \ + QEMU_GENERIC(x, \ + (QemuMutex *, qemu_mutex_lock), \ + (CoMutex *, qemu_co_mutex_lock), \ + (QemuSpin *, qemu_spin_lock), \ + unknown_lock_type)) + +#define QEMU_UNLOCK_FUNC(x) ((QemuLockUnlockFunc *) \ + QEMU_GENERIC(x, \ + (QemuMutex *, qemu_mutex_unlock), \ + (CoMutex *, qemu_co_mutex_unlock), \ + (QemuSpin *, qemu_spin_unlock), \ + unknown_lock_type)) + +/* In C, compound literals have the lifetime of an automatic variable. + * In C++ it would be different, but then C++ wouldn't need QemuLockable + * either... + */ +#define QEMU_MAKE_LOCKABLE_(x) qemu_make_lockable((x), &(QemuLockable) { \ + .object = (x), \ + .lock = QEMU_LOCK_FUNC(x), \ + .unlock = QEMU_UNLOCK_FUNC(x), \ + }) + +/* QEMU_MAKE_LOCKABLE - Make a polymorphic QemuLockable + * + * @x: a lock object (currently one of QemuMutex, CoMutex, QemuSpin). + * + * Returns a QemuLockable object that can be passed around + * to a function that can operate with locks of any kind. + */ +#define QEMU_MAKE_LOCKABLE(x) \ + QEMU_GENERIC(x, \ + (QemuLockable *, (x)), \ + QEMU_MAKE_LOCKABLE_(x)) + +static inline void qemu_lockable_lock(QemuLockable *x) +{ + x->lock(x->object); +} + +static inline void qemu_lockable_unlock(QemuLockable *x) +{ + x->unlock(x->object); +} + +#endif diff --git a/include/qemu/thread.h b/include/qemu/thread.h index 9af4e945aa..ef7bd16123 100644 --- a/include/qemu/thread.h +++ b/include/qemu/thread.h @@ -4,7 +4,6 @@ #include "qemu/processor.h" #include "qemu/atomic.h" -typedef struct QemuMutex QemuMutex; typedef struct QemuCond QemuCond; typedef struct QemuSemaphore QemuSemaphore; typedef struct QemuEvent QemuEvent; @@ -97,9 +96,9 @@ struct Notifier; void qemu_thread_atexit_add(struct Notifier *notifier); void qemu_thread_atexit_remove(struct Notifier *notifier); -typedef struct QemuSpin { +struct QemuSpin { int value; -} QemuSpin; +}; static inline void qemu_spin_init(QemuSpin *spin) { diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h index 9bd7a834ba..5923849cdd 100644 --- a/include/qemu/typedefs.h +++ b/include/qemu/typedefs.h @@ -19,6 +19,7 @@ typedef struct BusClass BusClass; typedef struct BusState BusState; typedef struct Chardev Chardev; typedef struct CompatProperty CompatProperty; +typedef struct CoMutex CoMutex; typedef struct CPUAddressSpace CPUAddressSpace; typedef struct CPUState CPUState; typedef struct DeviceListener DeviceListener; @@ -86,9 +87,12 @@ typedef struct QEMUBH QEMUBH; typedef struct QemuConsole QemuConsole; typedef struct QemuDmaBuf QemuDmaBuf; typedef struct QEMUFile QEMUFile; +typedef struct QemuLockable QemuLockable; +typedef struct QemuMutex QemuMutex; typedef struct QemuOpt QemuOpt; typedef struct QemuOpts QemuOpts; typedef struct QemuOptsList QemuOptsList; +typedef struct QemuSpin QemuSpin; typedef struct QEMUSGList QEMUSGList; typedef struct QEMUTimer QEMUTimer; typedef struct QEMUTimerListGroup QEMUTimerListGroup; diff --git a/tests/test-coroutine.c b/tests/test-coroutine.c index 010cb95ad6..6e4842bfda 100644 --- a/tests/test-coroutine.c +++ b/tests/test-coroutine.c @@ -14,6 +14,7 @@ #include "qemu/osdep.h" #include "qemu/coroutine.h" #include "qemu/coroutine_int.h" +#include "qemu/lockable.h" /* * Check that qemu_in_coroutine() works @@ -210,6 +211,18 @@ static void coroutine_fn mutex_fn(void *opaque) done++; } +static void coroutine_fn lockable_fn(void *opaque) +{ + QemuLockable *x = opaque; + qemu_lockable_lock(x); + assert(!locked); + locked = true; + qemu_coroutine_yield(); + locked = false; + qemu_lockable_unlock(x); + done++; +} + static void do_test_co_mutex(CoroutineEntry *entry, void *opaque) { Coroutine *c1 = qemu_coroutine_create(entry, opaque); @@ -240,6 +253,17 @@ static void test_co_mutex(void) do_test_co_mutex(mutex_fn, &m); } +static void test_co_mutex_lockable(void) +{ + CoMutex m; + CoMutex *null_pointer = NULL; + + qemu_co_mutex_init(&m); + do_test_co_mutex(lockable_fn, QEMU_MAKE_LOCKABLE(&m)); + + g_assert(QEMU_MAKE_LOCKABLE(null_pointer) == NULL); +} + /* * Check that creation, enter, and return work */ @@ -478,6 +502,7 @@ int main(int argc, char **argv) g_test_add_func("/basic/in_coroutine", test_in_coroutine); g_test_add_func("/basic/order", test_order); g_test_add_func("/locking/co-mutex", test_co_mutex); + g_test_add_func("/locking/co-mutex/lockable", test_co_mutex_lockable); if (g_test_perf()) { g_test_add_func("/perf/lifecycle", perf_lifecycle); g_test_add_func("/perf/nesting", perf_nesting); -- 2.14.3 ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH 2/5] lockable: add QemuLockable 2018-02-03 15:39 ` [Qemu-devel] [PATCH 2/5] lockable: add QemuLockable Paolo Bonzini @ 2018-02-03 20:44 ` Richard Henderson 2018-02-05 14:38 ` Paolo Bonzini 0 siblings, 1 reply; 19+ messages in thread From: Richard Henderson @ 2018-02-03 20:44 UTC (permalink / raw) To: Paolo Bonzini, qemu-devel; +Cc: famz, qemu-block, stefanha On 02/03/2018 07:39 AM, Paolo Bonzini wrote: > +/* This function gives an error if an invalid, non-NULL pointer type is passed > + * to QEMU_MAKE_LOCKABLE. For optimized builds, we can rely on dead-code elimination > + * from the compiler, and give the errors already at link time. > + */ > +#ifdef __OPTIMIZE__ > +void unknown_lock_type(void *); > +#else > +static inline void unknown_lock_type(void *unused) > +{ > + abort(); > +} Since you're using __builtin_choose_expr, I'm surprised you would need to test __OPTIMZE__. The nature of the builtin is such that it *must* eliminate the other branch; otherwise the types don't even match up. It might be worth using __attribute__((error("message"))) on the function too. Otherwise, Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~ ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH 2/5] lockable: add QemuLockable 2018-02-03 20:44 ` Richard Henderson @ 2018-02-05 14:38 ` Paolo Bonzini 0 siblings, 0 replies; 19+ messages in thread From: Paolo Bonzini @ 2018-02-05 14:38 UTC (permalink / raw) To: Richard Henderson, qemu-devel; +Cc: famz, qemu-block, stefanha On 03/02/2018 21:44, Richard Henderson wrote: > On 02/03/2018 07:39 AM, Paolo Bonzini wrote: >> +/* This function gives an error if an invalid, non-NULL pointer type is passed >> + * to QEMU_MAKE_LOCKABLE. For optimized builds, we can rely on dead-code elimination >> + * from the compiler, and give the errors already at link time. >> + */ >> +#ifdef __OPTIMIZE__ >> +void unknown_lock_type(void *); >> +#else >> +static inline void unknown_lock_type(void *unused) >> +{ >> + abort(); >> +} > > Since you're using __builtin_choose_expr, I'm surprised you would need to test > __OPTIMZE__. The nature of the builtin is such that it *must* eliminate the > other branch; otherwise the types don't even match up. __builtin_choose_expr works fine. However we also have return x ? __builtin_choose_expr(..., unknown_lock_type) : NULL; and if "x" is NULL then its type is a void*, and the LHS will refer to unknown_lock_type. I was expecting __always_inline__ to be enough to avoid this, but apparently this is not the case. Paolo > It might be worth using __attribute__((error("message"))) on the function too. > > Otherwise, > > Reviewed-by: Richard Henderson <richard.henderson@linaro.org> > > > r~ > ^ permalink raw reply [flat|nested] 19+ messages in thread
* [Qemu-devel] [PATCH 3/5] coroutine-lock: convert CoQueue to use QemuLockable 2018-02-03 15:39 [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini 2018-02-03 15:39 ` [Qemu-devel] [PATCH 1/5] test-coroutine: add simple CoMutex test Paolo Bonzini 2018-02-03 15:39 ` [Qemu-devel] [PATCH 2/5] lockable: add QemuLockable Paolo Bonzini @ 2018-02-03 15:39 ` Paolo Bonzini 2018-02-03 20:50 ` Richard Henderson 2018-02-03 15:39 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini ` (3 subsequent siblings) 6 siblings, 1 reply; 19+ messages in thread From: Paolo Bonzini @ 2018-02-03 15:39 UTC (permalink / raw) To: qemu-devel; +Cc: famz, stefanha, qemu-block There are cases in which a queued coroutine must be restarted from non-coroutine context (with qemu_co_enter_next). In this cases, qemu_co_enter_next also needs to be thread-safe, but it cannot use a CoMutex and so cannot qemu_co_queue_wait. Use QemuLockable so that the CoQueue can interchangeably use CoMutex or QemuMutex. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- include/qemu/coroutine.h | 6 +++++- util/qemu-coroutine-lock.c | 12 +++++++----- 2 files changed, 12 insertions(+), 6 deletions(-) diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h index 8a5129741c..1e5f0957e6 100644 --- a/include/qemu/coroutine.h +++ b/include/qemu/coroutine.h @@ -183,7 +183,9 @@ void qemu_co_queue_init(CoQueue *queue); * caller of the coroutine. The mutex is unlocked during the wait and * locked again afterwards. */ -void coroutine_fn qemu_co_queue_wait(CoQueue *queue, CoMutex *mutex); +#define qemu_co_queue_wait(queue, lock) \ + qemu_co_queue_wait_impl(queue, QEMU_MAKE_LOCKABLE(lock)) +void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock); /** * Restarts the next coroutine in the CoQueue and removes it from the queue. @@ -271,4 +273,6 @@ void coroutine_fn qemu_co_sleep_ns(QEMUClockType type, int64_t ns); */ void coroutine_fn yield_until_fd_readable(int fd); +#include "qemu/lockable.h" + #endif /* QEMU_COROUTINE_H */ diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c index 846ff9167f..2a66fc1467 100644 --- a/util/qemu-coroutine-lock.c +++ b/util/qemu-coroutine-lock.c @@ -40,13 +40,13 @@ void qemu_co_queue_init(CoQueue *queue) QSIMPLEQ_INIT(&queue->entries); } -void coroutine_fn qemu_co_queue_wait(CoQueue *queue, CoMutex *mutex) +void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock) { Coroutine *self = qemu_coroutine_self(); QSIMPLEQ_INSERT_TAIL(&queue->entries, self, co_queue_next); - if (mutex) { - qemu_co_mutex_unlock(mutex); + if (lock) { + qemu_lockable_unlock(lock); } /* There is no race condition here. Other threads will call @@ -60,9 +60,11 @@ void coroutine_fn qemu_co_queue_wait(CoQueue *queue, CoMutex *mutex) /* TODO: OSv implements wait morphing here, where the wakeup * primitive automatically places the woken coroutine on the * mutex's queue. This avoids the thundering herd effect. + * This could be implemented for CoMutexes, but not really for + * other cases of QemuLockable. */ - if (mutex) { - qemu_co_mutex_lock(mutex); + if (lock) { + qemu_lockable_lock(lock); } } -- 2.14.3 ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH 3/5] coroutine-lock: convert CoQueue to use QemuLockable 2018-02-03 15:39 ` [Qemu-devel] [PATCH 3/5] coroutine-lock: convert CoQueue to use QemuLockable Paolo Bonzini @ 2018-02-03 20:50 ` Richard Henderson 0 siblings, 0 replies; 19+ messages in thread From: Richard Henderson @ 2018-02-03 20:50 UTC (permalink / raw) To: Paolo Bonzini, qemu-devel; +Cc: famz, qemu-block, stefanha On 02/03/2018 07:39 AM, Paolo Bonzini wrote: > There are cases in which a queued coroutine must be restarted from > non-coroutine context (with qemu_co_enter_next). In this cases, > qemu_co_enter_next also needs to be thread-safe, but it cannot use > a CoMutex and so cannot qemu_co_queue_wait. Use QemuLockable so > that the CoQueue can interchangeably use CoMutex or QemuMutex. > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > include/qemu/coroutine.h | 6 +++++- > util/qemu-coroutine-lock.c | 12 +++++++----- > 2 files changed, 12 insertions(+), 6 deletions(-) Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~ ^ permalink raw reply [flat|nested] 19+ messages in thread
* [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe 2018-02-03 15:39 [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini ` (2 preceding siblings ...) 2018-02-03 15:39 ` [Qemu-devel] [PATCH 3/5] coroutine-lock: convert CoQueue to use QemuLockable Paolo Bonzini @ 2018-02-03 15:39 ` Paolo Bonzini 2018-02-03 20:57 ` Richard Henderson 2018-02-03 15:39 ` [Qemu-devel] [PATCH 5/5] curl: convert to CoQueue Paolo Bonzini ` (2 subsequent siblings) 6 siblings, 1 reply; 19+ messages in thread From: Paolo Bonzini @ 2018-02-03 15:39 UTC (permalink / raw) To: qemu-devel; +Cc: famz, stefanha, qemu-block qemu_co_queue_next does not need to release and re-acquire the mutex, because the queued coroutine does not run immediately. However, this does not hold for qemu_co_enter_next. Now that qemu_co_queue_wait can synchronize (via QemuLockable) with code that is not running in coroutine context, it's important that code using qemu_co_enter_next can easily use a standardized locking idiom. First of all, qemu_co_enter_next must use aio_co_wake to restart the coroutine. Second, the function gains a second argument, a QemuLockable*, and the comments of qemu_co_queue_next and qemu_co_queue_restart_all are adjusted to clarify the difference. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- fsdev/qemu-fsdev-throttle.c | 4 ++-- include/qemu/coroutine.h | 19 +++++++++++++------ util/qemu-coroutine-lock.c | 10 ++++++++-- 3 files changed, 23 insertions(+), 10 deletions(-) diff --git a/fsdev/qemu-fsdev-throttle.c b/fsdev/qemu-fsdev-throttle.c index 49eebb5412..1dc07fbc12 100644 --- a/fsdev/qemu-fsdev-throttle.c +++ b/fsdev/qemu-fsdev-throttle.c @@ -20,13 +20,13 @@ static void fsdev_throttle_read_timer_cb(void *opaque) { FsThrottle *fst = opaque; - qemu_co_enter_next(&fst->throttled_reqs[false]); + qemu_co_enter_next(&fst->throttled_reqs[false], NULL); } static void fsdev_throttle_write_timer_cb(void *opaque) { FsThrottle *fst = opaque; - qemu_co_enter_next(&fst->throttled_reqs[true]); + qemu_co_enter_next(&fst->throttled_reqs[true], NULL); } void fsdev_throttle_parse_opts(QemuOpts *opts, FsThrottle *fst, Error **errp) diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h index 1e5f0957e6..3afee7169b 100644 --- a/include/qemu/coroutine.h +++ b/include/qemu/coroutine.h @@ -188,21 +188,28 @@ void qemu_co_queue_init(CoQueue *queue); void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock); /** - * Restarts the next coroutine in the CoQueue and removes it from the queue. - * - * Returns true if a coroutine was restarted, false if the queue is empty. + * Removes the next coroutine from the CoQueue, and wake it up. + * Returns true if a coroutine was removed, false if the queue is empty. */ bool coroutine_fn qemu_co_queue_next(CoQueue *queue); /** - * Restarts all coroutines in the CoQueue and leaves the queue empty. + * Empties the CoQueue; all coroutines are woken up. */ void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue); /** - * Enter the next coroutine in the queue + * Removes the next coroutine from the CoQueue, and wake it up. Unlike + * qemu_co_queue_next, this function releases the lock during aio_co_wake + * because it is meant to be used outside coroutine context; in that case, the + * coroutine is entered immediately, before qemu_co_enter_next returns. + * + * If used in coroutine context, qemu_co_enter_next is equivalent to + * qemu_co_queue_next. */ -bool qemu_co_enter_next(CoQueue *queue); +#define qemu_co_enter_next(queue, lock) \ + qemu_co_enter_next_impl(queue, QEMU_MAKE_LOCKABLE(lock)) +bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock); /** * Checks if the CoQueue is empty. diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c index 2a66fc1467..78fb79acf8 100644 --- a/util/qemu-coroutine-lock.c +++ b/util/qemu-coroutine-lock.c @@ -132,7 +132,7 @@ void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue) qemu_co_queue_do_restart(queue, false); } -bool qemu_co_enter_next(CoQueue *queue) +bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock) { Coroutine *next; @@ -142,7 +142,13 @@ bool qemu_co_enter_next(CoQueue *queue) } QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next); - qemu_coroutine_enter(next); + if (lock) { + qemu_lockable_unlock(lock); + } + aio_co_wake(next); + if (lock) { + qemu_lockable_lock(lock); + } return true; } -- 2.14.3 ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe 2018-02-03 15:39 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini @ 2018-02-03 20:57 ` Richard Henderson 0 siblings, 0 replies; 19+ messages in thread From: Richard Henderson @ 2018-02-03 20:57 UTC (permalink / raw) To: Paolo Bonzini, qemu-devel; +Cc: famz, qemu-block, stefanha On 02/03/2018 07:39 AM, Paolo Bonzini wrote: > qemu_co_queue_next does not need to release and re-acquire the mutex, > because the queued coroutine does not run immediately. However, this > does not hold for qemu_co_enter_next. Now that qemu_co_queue_wait > can synchronize (via QemuLockable) with code that is not running in > coroutine context, it's important that code using qemu_co_enter_next > can easily use a standardized locking idiom. > > First of all, qemu_co_enter_next must use aio_co_wake to restart the > coroutine. Second, the function gains a second argument, a QemuLockable*, > and the comments of qemu_co_queue_next and qemu_co_queue_restart_all > are adjusted to clarify the difference. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > fsdev/qemu-fsdev-throttle.c | 4 ++-- > include/qemu/coroutine.h | 19 +++++++++++++------ > util/qemu-coroutine-lock.c | 10 ++++++++-- > 3 files changed, 23 insertions(+), 10 deletions(-) Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~ ^ permalink raw reply [flat|nested] 19+ messages in thread
* [Qemu-devel] [PATCH 5/5] curl: convert to CoQueue 2018-02-03 15:39 [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini ` (3 preceding siblings ...) 2018-02-03 15:39 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini @ 2018-02-03 15:39 ` Paolo Bonzini 2018-02-03 20:59 ` Richard Henderson 2018-02-05 14:39 ` [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Stefan Hajnoczi 2018-02-07 5:27 ` Fam Zheng 6 siblings, 1 reply; 19+ messages in thread From: Paolo Bonzini @ 2018-02-03 15:39 UTC (permalink / raw) To: qemu-devel; +Cc: famz, stefanha, qemu-block Now that CoQueues can use a QemuMutex for thread-safety, there is no need for curl to roll its own coroutine queue. Coroutines can be placed directly on the queue instead of using a list of CURLAIOCBs. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- block/curl.c | 20 ++++---------------- 1 file changed, 4 insertions(+), 16 deletions(-) diff --git a/block/curl.c b/block/curl.c index 35cf417f59..cd578d3d14 100644 --- a/block/curl.c +++ b/block/curl.c @@ -101,8 +101,6 @@ typedef struct CURLAIOCB { size_t start; size_t end; - - QSIMPLEQ_ENTRY(CURLAIOCB) next; } CURLAIOCB; typedef struct CURLSocket { @@ -138,7 +136,7 @@ typedef struct BDRVCURLState { bool accept_range; AioContext *aio_context; QemuMutex mutex; - QSIMPLEQ_HEAD(, CURLAIOCB) free_state_waitq; + CoQueue free_state_waitq; char *username; char *password; char *proxyusername; @@ -538,7 +536,6 @@ static int curl_init_state(BDRVCURLState *s, CURLState *state) /* Called with s->mutex held. */ static void curl_clean_state(CURLState *s) { - CURLAIOCB *next; int j; for (j = 0; j < CURL_NUM_ACB; j++) { assert(!s->acb[j]); @@ -556,13 +553,7 @@ static void curl_clean_state(CURLState *s) s->in_use = 0; - next = QSIMPLEQ_FIRST(&s->s->free_state_waitq); - if (next) { - QSIMPLEQ_REMOVE_HEAD(&s->s->free_state_waitq, next); - qemu_mutex_unlock(&s->s->mutex); - aio_co_wake(next->co); - qemu_mutex_lock(&s->s->mutex); - } + qemu_co_enter_next(&s->s->free_state_waitq, &s->s->mutex); } static void curl_parse_filename(const char *filename, QDict *options, @@ -784,7 +775,7 @@ static int curl_open(BlockDriverState *bs, QDict *options, int flags, } DPRINTF("CURL: Opening %s\n", file); - QSIMPLEQ_INIT(&s->free_state_waitq); + qemu_co_queue_init(&s->free_state_waitq); s->aio_context = bdrv_get_aio_context(bs); s->url = g_strdup(file); qemu_mutex_lock(&s->mutex); @@ -888,10 +879,7 @@ static void curl_setup_preadv(BlockDriverState *bs, CURLAIOCB *acb) if (state) { break; } - QSIMPLEQ_INSERT_TAIL(&s->free_state_waitq, acb, next); - qemu_mutex_unlock(&s->mutex); - qemu_coroutine_yield(); - qemu_mutex_lock(&s->mutex); + qemu_co_queue_wait(&s->free_state_waitq, &s->mutex); } if (curl_init_state(s, state) < 0) { -- 2.14.3 ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH 5/5] curl: convert to CoQueue 2018-02-03 15:39 ` [Qemu-devel] [PATCH 5/5] curl: convert to CoQueue Paolo Bonzini @ 2018-02-03 20:59 ` Richard Henderson 0 siblings, 0 replies; 19+ messages in thread From: Richard Henderson @ 2018-02-03 20:59 UTC (permalink / raw) To: Paolo Bonzini, qemu-devel; +Cc: famz, qemu-block, stefanha On 02/03/2018 07:39 AM, Paolo Bonzini wrote: > Now that CoQueues can use a QemuMutex for thread-safety, there is no > need for curl to roll its own coroutine queue. Coroutines can be > placed directly on the queue instead of using a list of CURLAIOCBs. > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > block/curl.c | 20 ++++---------------- > 1 file changed, 4 insertions(+), 16 deletions(-) Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~ ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue 2018-02-03 15:39 [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini ` (4 preceding siblings ...) 2018-02-03 15:39 ` [Qemu-devel] [PATCH 5/5] curl: convert to CoQueue Paolo Bonzini @ 2018-02-05 14:39 ` Stefan Hajnoczi 2018-02-07 5:27 ` Fam Zheng 6 siblings, 0 replies; 19+ messages in thread From: Stefan Hajnoczi @ 2018-02-05 14:39 UTC (permalink / raw) To: Paolo Bonzini; +Cc: qemu-devel, famz, qemu-block [-- Attachment #1: Type: text/plain, Size: 2118 bytes --] On Sat, Feb 03, 2018 at 10:39:30AM -0500, Paolo Bonzini wrote: > There are cases in which a queued coroutine must be restarted from > non-coroutine context (with qemu_co_enter_next). In this cases, > qemu_co_enter_next also needs to be thread-safe, but it cannot use a > CoMutex and so cannot qemu_co_queue_wait. This happens in curl (which > right now is rolling its own list of Coroutines) and will happen in > Fam's NVMe driver as well. > > This series extracts the idea of a polymorphic lockable object > from my "scoped lock guard" proposal, and applies it to CoQueue. > The implementation of QemuLockable is similar to C11 _Generic, but > redone using the preprocessor and GCC builtins for compatibility. > > In general, while a bit on the esoteric side, the functionality used > to emulate _Generic is fairly old in GCC, and the builtins are already > used by include/qemu/atomic.h; the series was tested with Fedora 27 (boot > Damn Small Linux via http) and CentOS 6 (compiled only). > > Paolo > > v4->v5: fix checkpatch complaints > > v3->v4: fix -O0 compilation [Fam] > typos and copyright dates [Eric, Fam] > improve CoQueue comments [Stefan] > > Paolo Bonzini (5): > test-coroutine: add simple CoMutex test > lockable: add QemuLockable > coroutine-lock: convert CoQueue to use QemuLockable > coroutine-lock: make qemu_co_enter_next thread-safe > curl: convert to CoQueue > > block/curl.c | 20 ++-------- > fsdev/qemu-fsdev-throttle.c | 4 +- > include/qemu/compiler.h | 40 +++++++++++++++++++ > include/qemu/coroutine.h | 29 +++++++++----- > include/qemu/lockable.h | 96 +++++++++++++++++++++++++++++++++++++++++++++ > include/qemu/thread.h | 5 +-- > include/qemu/typedefs.h | 4 ++ > tests/test-coroutine.c | 75 ++++++++++++++++++++++++++++++++++- > util/qemu-coroutine-lock.c | 22 +++++++---- > 9 files changed, 256 insertions(+), 39 deletions(-) > create mode 100644 include/qemu/lockable.h > > -- > 2.14.3 > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 455 bytes --] ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue 2018-02-03 15:39 [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini ` (5 preceding siblings ...) 2018-02-05 14:39 ` [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Stefan Hajnoczi @ 2018-02-07 5:27 ` Fam Zheng 6 siblings, 0 replies; 19+ messages in thread From: Fam Zheng @ 2018-02-07 5:27 UTC (permalink / raw) To: Paolo Bonzini; +Cc: qemu-devel, stefanha, qemu-block On Sat, 02/03 10:39, Paolo Bonzini wrote: > There are cases in which a queued coroutine must be restarted from > non-coroutine context (with qemu_co_enter_next). In this cases, > qemu_co_enter_next also needs to be thread-safe, but it cannot use a > CoMutex and so cannot qemu_co_queue_wait. This happens in curl (which > right now is rolling its own list of Coroutines) and will happen in > Fam's NVMe driver as well. > > This series extracts the idea of a polymorphic lockable object > from my "scoped lock guard" proposal, and applies it to CoQueue. > The implementation of QemuLockable is similar to C11 _Generic, but > redone using the preprocessor and GCC builtins for compatibility. > > In general, while a bit on the esoteric side, the functionality used > to emulate _Generic is fairly old in GCC, and the builtins are already > used by include/qemu/atomic.h; the series was tested with Fedora 27 (boot > Damn Small Linux via http) and CentOS 6 (compiled only). > > Paolo > > v4->v5: fix checkpatch complaints Queued, thanks. Fam ^ permalink raw reply [flat|nested] 19+ messages in thread
* [Qemu-devel] [PATCH v4 0/5] coroutine-lock: polymorphic CoQueue @ 2018-02-01 21:29 Paolo Bonzini 2018-02-01 21:29 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini 0 siblings, 1 reply; 19+ messages in thread From: Paolo Bonzini @ 2018-02-01 21:29 UTC (permalink / raw) To: qemu-devel; +Cc: famz, stefanha, qemu-block There are cases in which a queued coroutine must be restarted from non-coroutine context (with qemu_co_enter_next). In this cases, qemu_co_enter_next also needs to be thread-safe, but it cannot use a CoMutex and so cannot qemu_co_queue_wait. This happens in curl (which right now is rolling its own list of Coroutines) and will happen in Fam's NVMe driver as well. This series extracts the idea of a polymorphic lockable object from my "scoped lock guard" proposal, and applies it to CoQueue. The implementation of QemuLockable is similar to C11 _Generic, but redone using the preprocessor and GCC builtins for compatibility. In general, while a bit on the esoteric side, the functionality used to emulate _Generic is fairly old in GCC, and the builtins are already used by include/qemu/atomic.h; the series was tested with Fedora 27 (boot Damn Small Linux via http) and CentOS 6 (compiled only). Paolo v3->v4: fix -O0 compilation [Fam] typos and copyright dates [Eric, Fam] improve CoQueue comments [Stefan] Paolo Bonzini (5): test-coroutine: add simple CoMutex test lockable: add QemuLockable coroutine-lock: convert CoQueue to use QemuLockable coroutine-lock: make qemu_co_enter_next thread-safe curl: convert to CoQueue block/curl.c | 20 ++-------- fsdev/qemu-fsdev-throttle.c | 4 +- include/qemu/compiler.h | 40 +++++++++++++++++++ include/qemu/coroutine.h | 29 +++++++++----- include/qemu/lockable.h | 96 +++++++++++++++++++++++++++++++++++++++++++++ include/qemu/thread.h | 5 +-- include/qemu/typedefs.h | 4 ++ tests/test-coroutine.c | 75 ++++++++++++++++++++++++++++++++++- util/qemu-coroutine-lock.c | 22 +++++++---- 9 files changed, 256 insertions(+), 39 deletions(-) create mode 100644 include/qemu/lockable.h -- 2.14.3 ^ permalink raw reply [flat|nested] 19+ messages in thread
* [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe 2018-02-01 21:29 [Qemu-devel] [PATCH v4 " Paolo Bonzini @ 2018-02-01 21:29 ` Paolo Bonzini 0 siblings, 0 replies; 19+ messages in thread From: Paolo Bonzini @ 2018-02-01 21:29 UTC (permalink / raw) To: qemu-devel; +Cc: famz, stefanha, qemu-block qemu_co_queue_next does not need to release and re-acquire the mutex, because the queued coroutine does not run immediately. However, this does not hold for qemu_co_enter_next. Now that qemu_co_queue_wait can synchronize (via QemuLockable) with code that is not running in coroutine context, it's important that code using qemu_co_enter_next can easily use a standardized locking idiom. First of all, qemu_co_enter_next must use aio_co_wake to restart the coroutine. Second, the function gains a second argument, a QemuLockable*, and the comments of qemu_co_queue_next and qemu_co_queue_restart_all are adjusted to clarify the difference. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- fsdev/qemu-fsdev-throttle.c | 4 ++-- include/qemu/coroutine.h | 19 +++++++++++++------ util/qemu-coroutine-lock.c | 10 ++++++++-- 3 files changed, 23 insertions(+), 10 deletions(-) diff --git a/fsdev/qemu-fsdev-throttle.c b/fsdev/qemu-fsdev-throttle.c index 49eebb5412..1dc07fbc12 100644 --- a/fsdev/qemu-fsdev-throttle.c +++ b/fsdev/qemu-fsdev-throttle.c @@ -20,13 +20,13 @@ static void fsdev_throttle_read_timer_cb(void *opaque) { FsThrottle *fst = opaque; - qemu_co_enter_next(&fst->throttled_reqs[false]); + qemu_co_enter_next(&fst->throttled_reqs[false], NULL); } static void fsdev_throttle_write_timer_cb(void *opaque) { FsThrottle *fst = opaque; - qemu_co_enter_next(&fst->throttled_reqs[true]); + qemu_co_enter_next(&fst->throttled_reqs[true], NULL); } void fsdev_throttle_parse_opts(QemuOpts *opts, FsThrottle *fst, Error **errp) diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h index 1e5f0957e6..3afee7169b 100644 --- a/include/qemu/coroutine.h +++ b/include/qemu/coroutine.h @@ -188,21 +188,28 @@ void qemu_co_queue_init(CoQueue *queue); void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock); /** - * Restarts the next coroutine in the CoQueue and removes it from the queue. - * - * Returns true if a coroutine was restarted, false if the queue is empty. + * Removes the next coroutine from the CoQueue, and wake it up. + * Returns true if a coroutine was removed, false if the queue is empty. */ bool coroutine_fn qemu_co_queue_next(CoQueue *queue); /** - * Restarts all coroutines in the CoQueue and leaves the queue empty. + * Empties the CoQueue; all coroutines are woken up. */ void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue); /** - * Enter the next coroutine in the queue + * Removes the next coroutine from the CoQueue, and wake it up. Unlike + * qemu_co_queue_next, this function releases the lock during aio_co_wake + * because it is meant to be used outside coroutine context; in that case, the + * coroutine is entered immediately, before qemu_co_enter_next returns. + * + * If used in coroutine context, qemu_co_enter_next is equivalent to + * qemu_co_queue_next. */ -bool qemu_co_enter_next(CoQueue *queue); +#define qemu_co_enter_next(queue, lock) \ + qemu_co_enter_next_impl(queue, QEMU_MAKE_LOCKABLE(lock)) +bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock); /** * Checks if the CoQueue is empty. diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c index 2a66fc1467..78fb79acf8 100644 --- a/util/qemu-coroutine-lock.c +++ b/util/qemu-coroutine-lock.c @@ -132,7 +132,7 @@ void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue) qemu_co_queue_do_restart(queue, false); } -bool qemu_co_enter_next(CoQueue *queue) +bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock) { Coroutine *next; @@ -142,7 +142,13 @@ bool qemu_co_enter_next(CoQueue *queue) } QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next); - qemu_coroutine_enter(next); + if (lock) { + qemu_lockable_unlock(lock); + } + aio_co_wake(next); + if (lock) { + qemu_lockable_lock(lock); + } return true; } -- 2.14.3 ^ permalink raw reply related [flat|nested] 19+ messages in thread
* [Qemu-devel] [PATCH v3 0/5] coroutine-lock: polymorphic CoQueue @ 2018-01-25 17:59 Paolo Bonzini 2018-01-25 17:59 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini 0 siblings, 1 reply; 19+ messages in thread From: Paolo Bonzini @ 2018-01-25 17:59 UTC (permalink / raw) To: qemu-devel; +Cc: famz There are cases in which a queued coroutine must be restarted from non-coroutine context (with qemu_co_enter_next). In this cases, qemu_co_enter_next also needs to be thread-safe, but it cannot use a CoMutex and so cannot qemu_co_queue_wait. This happens in curl (which right now is rolling its own list of Coroutines) and will happen in Fam's NVMe driver as well. This series extracts the idea of a polymorphic lockable object from my "scoped lock guard" proposal, and applies it to CoQueue. The implementation of QemuLockable is similar to C11 _Generic, but redone using the preprocessor and GCC builtins for compatibility. In general, while a bit on the esoteric side, the functionality used to emulate _Generic is fairly old in GCC, and the builtins are already used by include/qemu/atomic.h; the series was tested with Fedora 27 (boot Damn Small Linux via http) and CentOS 6 (compiled only). Paolo v1->v2: fix typos and copyright year v2->v3: add tests, fix brown paper bag bug, avoid -Waddress errors Paolo Bonzini (5): test-coroutine: add simple CoMutex test lockable: add QemuLockable coroutine-lock: convert CoQueue to use QemuLockable coroutine-lock: make qemu_co_enter_next thread-safe curl: convert to CoQueue block/curl.c | 20 +++-------- fsdev/qemu-fsdev-throttle.c | 4 +-- include/qemu/compiler.h | 40 +++++++++++++++++++++ include/qemu/coroutine.h | 25 ++++++++----- include/qemu/lockable.h | 88 +++++++++++++++++++++++++++++++++++++++++++++ include/qemu/thread.h | 5 ++- include/qemu/typedefs.h | 4 +++ tests/test-coroutine.c | 75 ++++++++++++++++++++++++++++++++++++-- util/qemu-coroutine-lock.c | 22 ++++++++---- 9 files changed, 245 insertions(+), 38 deletions(-) create mode 100644 include/qemu/lockable.h -- 2.14.3 ^ permalink raw reply [flat|nested] 19+ messages in thread
* [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe 2018-01-25 17:59 [Qemu-devel] [PATCH v3 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini @ 2018-01-25 17:59 ` Paolo Bonzini 2018-01-25 20:15 ` Eric Blake 2018-01-29 13:26 ` Stefan Hajnoczi 0 siblings, 2 replies; 19+ messages in thread From: Paolo Bonzini @ 2018-01-25 17:59 UTC (permalink / raw) To: qemu-devel; +Cc: famz qemu_co_queue_next does not need to release and re-acquire the mutex, because the queued coroutine does not run immediately. However, this does not hold for qemu_co_enter_next. Now that qemu_co_queue_wait can synchronize (via QemuLockable) with code that is not running in coroutine context, it's important that code using qemu_co_enter_next can easily use a standardized locking idiom. First of all, qemu_co_enter_next must use aio_co_wake to restart the coroutine. Second, the function gains a second argument, a QemuLockable*, and the comments of qemu_co_queue_next and qemu_co_queue_restart_all are adjusted to clarify the difference. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- fsdev/qemu-fsdev-throttle.c | 4 ++-- include/qemu/coroutine.h | 15 ++++++++++----- util/qemu-coroutine-lock.c | 10 ++++++++-- 3 files changed, 20 insertions(+), 9 deletions(-) diff --git a/fsdev/qemu-fsdev-throttle.c b/fsdev/qemu-fsdev-throttle.c index 49eebb5412..1dc07fbc12 100644 --- a/fsdev/qemu-fsdev-throttle.c +++ b/fsdev/qemu-fsdev-throttle.c @@ -20,13 +20,13 @@ static void fsdev_throttle_read_timer_cb(void *opaque) { FsThrottle *fst = opaque; - qemu_co_enter_next(&fst->throttled_reqs[false]); + qemu_co_enter_next(&fst->throttled_reqs[false], NULL); } static void fsdev_throttle_write_timer_cb(void *opaque) { FsThrottle *fst = opaque; - qemu_co_enter_next(&fst->throttled_reqs[true]); + qemu_co_enter_next(&fst->throttled_reqs[true], NULL); } void fsdev_throttle_parse_opts(QemuOpts *opts, FsThrottle *fst, Error **errp) diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h index 1e5f0957e6..6fdbc837c0 100644 --- a/include/qemu/coroutine.h +++ b/include/qemu/coroutine.h @@ -188,21 +188,26 @@ void qemu_co_queue_init(CoQueue *queue); void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock); /** - * Restarts the next coroutine in the CoQueue and removes it from the queue. + * Removes the next coroutine from the CoQueue; it will run as soon as the + * current one yields. * - * Returns true if a coroutine was restarted, false if the queue is empty. + * Returns true if a coroutine was removed, false if the queue is empty. */ bool coroutine_fn qemu_co_queue_next(CoQueue *queue); /** - * Restarts all coroutines in the CoQueue and leaves the queue empty. + * Empties the CoQueue; all coroutines in it will run in FIFO orer as soon + * as the current one yields. */ void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue); /** - * Enter the next coroutine in the queue + * Immediately enter the next coroutine in the queue. Release the mutex + * while it runs. */ -bool qemu_co_enter_next(CoQueue *queue); +#define qemu_co_enter_next(queue, lock) \ + qemu_co_enter_next_impl(queue, QEMU_MAKE_LOCKABLE(lock)) +bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock); /** * Checks if the CoQueue is empty. diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c index 2a66fc1467..78fb79acf8 100644 --- a/util/qemu-coroutine-lock.c +++ b/util/qemu-coroutine-lock.c @@ -132,7 +132,7 @@ void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue) qemu_co_queue_do_restart(queue, false); } -bool qemu_co_enter_next(CoQueue *queue) +bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock) { Coroutine *next; @@ -142,7 +142,13 @@ bool qemu_co_enter_next(CoQueue *queue) } QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next); - qemu_coroutine_enter(next); + if (lock) { + qemu_lockable_unlock(lock); + } + aio_co_wake(next); + if (lock) { + qemu_lockable_lock(lock); + } return true; } -- 2.14.3 ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe 2018-01-25 17:59 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini @ 2018-01-25 20:15 ` Eric Blake 2018-01-29 13:26 ` Stefan Hajnoczi 1 sibling, 0 replies; 19+ messages in thread From: Eric Blake @ 2018-01-25 20:15 UTC (permalink / raw) To: Paolo Bonzini, qemu-devel; +Cc: famz [-- Attachment #1: Type: text/plain, Size: 1210 bytes --] On 01/25/2018 11:59 AM, Paolo Bonzini wrote: > qemu_co_queue_next does not need to release and re-acquire the mutex, > because the queued coroutine does not run immediately. However, this > does not hold for qemu_co_enter_next. Now that qemu_co_queue_wait > can synchronize (via QemuLockable) with code that is not running in > coroutine context, it's important that code using qemu_co_enter_next > can easily use a standardized locking idiom. > > First of all, qemu_co_enter_next must use aio_co_wake to restart the > coroutine. Second, the function gains a second argument, a QemuLockable*, > and the comments of qemu_co_queue_next and qemu_co_queue_restart_all > are adjusted to clarify the difference. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > /** > - * Restarts all coroutines in the CoQueue and leaves the queue empty. > + * Empties the CoQueue; all coroutines in it will run in FIFO orer as soon s/orer/order/ > + * as the current one yields. > */ > void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue); -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 619 bytes --] ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe 2018-01-25 17:59 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini 2018-01-25 20:15 ` Eric Blake @ 2018-01-29 13:26 ` Stefan Hajnoczi 2018-02-01 15:28 ` Paolo Bonzini 1 sibling, 1 reply; 19+ messages in thread From: Stefan Hajnoczi @ 2018-01-29 13:26 UTC (permalink / raw) To: Paolo Bonzini; +Cc: qemu-devel, famz [-- Attachment #1: Type: text/plain, Size: 4643 bytes --] On Thu, Jan 25, 2018 at 06:59:48PM +0100, Paolo Bonzini wrote: > qemu_co_queue_next does not need to release and re-acquire the mutex, > because the queued coroutine does not run immediately. However, this > does not hold for qemu_co_enter_next. Now that qemu_co_queue_wait > can synchronize (via QemuLockable) with code that is not running in > coroutine context, it's important that code using qemu_co_enter_next > can easily use a standardized locking idiom. > > First of all, qemu_co_enter_next must use aio_co_wake to restart the > coroutine. Second, the function gains a second argument, a QemuLockable*, > and the comments of qemu_co_queue_next and qemu_co_queue_restart_all > are adjusted to clarify the difference. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > fsdev/qemu-fsdev-throttle.c | 4 ++-- > include/qemu/coroutine.h | 15 ++++++++++----- > util/qemu-coroutine-lock.c | 10 ++++++++-- > 3 files changed, 20 insertions(+), 9 deletions(-) > > diff --git a/fsdev/qemu-fsdev-throttle.c b/fsdev/qemu-fsdev-throttle.c > index 49eebb5412..1dc07fbc12 100644 > --- a/fsdev/qemu-fsdev-throttle.c > +++ b/fsdev/qemu-fsdev-throttle.c > @@ -20,13 +20,13 @@ > static void fsdev_throttle_read_timer_cb(void *opaque) > { > FsThrottle *fst = opaque; > - qemu_co_enter_next(&fst->throttled_reqs[false]); > + qemu_co_enter_next(&fst->throttled_reqs[false], NULL); > } > > static void fsdev_throttle_write_timer_cb(void *opaque) > { > FsThrottle *fst = opaque; > - qemu_co_enter_next(&fst->throttled_reqs[true]); > + qemu_co_enter_next(&fst->throttled_reqs[true], NULL); > } > > void fsdev_throttle_parse_opts(QemuOpts *opts, FsThrottle *fst, Error **errp) > diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h > index 1e5f0957e6..6fdbc837c0 100644 > --- a/include/qemu/coroutine.h > +++ b/include/qemu/coroutine.h > @@ -188,21 +188,26 @@ void qemu_co_queue_init(CoQueue *queue); > void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock); > > /** > - * Restarts the next coroutine in the CoQueue and removes it from the queue. > + * Removes the next coroutine from the CoQueue; it will run as soon as the > + * current one yields. > * > - * Returns true if a coroutine was restarted, false if the queue is empty. > + * Returns true if a coroutine was removed, false if the queue is empty. > */ > bool coroutine_fn qemu_co_queue_next(CoQueue *queue); > > /** > - * Restarts all coroutines in the CoQueue and leaves the queue empty. > + * Empties the CoQueue; all coroutines in it will run in FIFO orer as soon > + * as the current one yields. > */ > void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue); > > /** > - * Enter the next coroutine in the queue > + * Immediately enter the next coroutine in the queue. Release the mutex > + * while it runs. s/mutex/lock/ Is this doc comment correct? I see multiple cases due to aio_co_wake(): 1. Called from coroutine context with current AioContext matching next coroutine's AioContext: arrange for next coroutine to be entered *after* we yield (not "immediately"). 2. Called from non-coroutine context with current AioContext matching next coroutine's AioContext: immediately enter next coroutine. 3. Called from different AioContext than next coroutine: arrange for next coroutine to be entered at some point. > */ > -bool qemu_co_enter_next(CoQueue *queue); > +#define qemu_co_enter_next(queue, lock) \ > + qemu_co_enter_next_impl(queue, QEMU_MAKE_LOCKABLE(lock)) > +bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock); > > /** > * Checks if the CoQueue is empty. > diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c > index 2a66fc1467..78fb79acf8 100644 > --- a/util/qemu-coroutine-lock.c > +++ b/util/qemu-coroutine-lock.c > @@ -132,7 +132,7 @@ void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue) > qemu_co_queue_do_restart(queue, false); > } > > -bool qemu_co_enter_next(CoQueue *queue) > +bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock) > { > Coroutine *next; > > @@ -142,7 +142,13 @@ bool qemu_co_enter_next(CoQueue *queue) > } > > QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next); > - qemu_coroutine_enter(next); > + if (lock) { > + qemu_lockable_unlock(lock); > + } > + aio_co_wake(next); > + if (lock) { > + qemu_lockable_lock(lock); > + } > return true; > } > > -- > 2.14.3 > > > [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 455 bytes --] ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe 2018-01-29 13:26 ` Stefan Hajnoczi @ 2018-02-01 15:28 ` Paolo Bonzini 0 siblings, 0 replies; 19+ messages in thread From: Paolo Bonzini @ 2018-02-01 15:28 UTC (permalink / raw) To: Stefan Hajnoczi; +Cc: famz, qemu-devel On 29/01/2018 08:26, Stefan Hajnoczi wrote: >> /** >> - * Enter the next coroutine in the queue >> + * Immediately enter the next coroutine in the queue. Release the mutex >> + * while it runs. > > s/mutex/lock/ > > Is this doc comment correct? I see multiple cases due to aio_co_wake(): > > 1. Called from coroutine context with current AioContext matching next > coroutine's AioContext: arrange for next coroutine to be entered > *after* we yield (not "immediately"). > > 2. Called from non-coroutine context with current AioContext matching > next coroutine's AioContext: immediately enter next coroutine. > > 3. Called from different AioContext than next coroutine: arrange for > next coroutine to be entered at some point. Good point, it needs to be more specific. Here is the best I could come up with: + * Removes the next coroutine from the CoQueue, and wake it up. * Returns true if a coroutine was removed, false if the queue is empty. */ bool coroutine_fn qemu_co_queue_next(CoQueue *queue); ... + * Empties the CoQueue; all coroutines are woken up. */ void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue); ... + * Removes the next coroutine from the CoQueue, and wake it up. Unlike + * qemu_co_queue_next, this function releases the lock during aio_co_wake + * because it is meant to be used outside coroutine context; in that case, the + * coroutine is entered immediately, before qemu_co_enter_next returns. + * + * If used in coroutine context, qemu_co_enter_next is equivalent to + * qemu_co_queue_next. */ #define qemu_co_enter_next(queue, lock) \ qemu_co_enter_next_impl(queue, QEMU_MAKE_LOCKABLE(lock)) ^ permalink raw reply [flat|nested] 19+ messages in thread
end of thread, other threads:[~2018-02-07 5:28 UTC | newest] Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2018-02-03 15:39 [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini 2018-02-03 15:39 ` [Qemu-devel] [PATCH 1/5] test-coroutine: add simple CoMutex test Paolo Bonzini 2018-02-03 20:46 ` Richard Henderson 2018-02-03 15:39 ` [Qemu-devel] [PATCH 2/5] lockable: add QemuLockable Paolo Bonzini 2018-02-03 20:44 ` Richard Henderson 2018-02-05 14:38 ` Paolo Bonzini 2018-02-03 15:39 ` [Qemu-devel] [PATCH 3/5] coroutine-lock: convert CoQueue to use QemuLockable Paolo Bonzini 2018-02-03 20:50 ` Richard Henderson 2018-02-03 15:39 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini 2018-02-03 20:57 ` Richard Henderson 2018-02-03 15:39 ` [Qemu-devel] [PATCH 5/5] curl: convert to CoQueue Paolo Bonzini 2018-02-03 20:59 ` Richard Henderson 2018-02-05 14:39 ` [Qemu-devel] [PATCH v5 0/5] coroutine-lock: polymorphic CoQueue Stefan Hajnoczi 2018-02-07 5:27 ` Fam Zheng -- strict thread matches above, loose matches on Subject: below -- 2018-02-01 21:29 [Qemu-devel] [PATCH v4 " Paolo Bonzini 2018-02-01 21:29 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini 2018-01-25 17:59 [Qemu-devel] [PATCH v3 0/5] coroutine-lock: polymorphic CoQueue Paolo Bonzini 2018-01-25 17:59 ` [Qemu-devel] [PATCH 4/5] coroutine-lock: make qemu_co_enter_next thread-safe Paolo Bonzini 2018-01-25 20:15 ` Eric Blake 2018-01-29 13:26 ` Stefan Hajnoczi 2018-02-01 15:28 ` Paolo Bonzini
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.