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From: Robert Foley <robert.foley@linaro.org>
To: qemu-devel@nongnu.org
Cc: richard.henderson@linaro.org, "Emilio G. Cota" <cota@braap.org>,
	alex.bennee@linaro.org, robert.foley@linaro.org,
	peter.puhov@linaro.org
Subject: [PATCH v8 03/74] cpu: introduce cpu_mutex_lock/unlock
Date: Thu, 26 Mar 2020 15:30:45 -0400
Message-ID: <20200326193156.4322-4-robert.foley@linaro.org> (raw)
In-Reply-To: <20200326193156.4322-1-robert.foley@linaro.org>

From: "Emilio G. Cota" <cota@braap.org>

The few direct users of &cpu->lock will be converted soon.

The per-thread bitmap introduced here might seem unnecessary,
since a bool could just do. However, once we complete the
conversion to per-vCPU locks, we will need to cover the use
case where all vCPUs are locked by the same thread, which
explains why the bitmap is introduced here.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Robert Foley <robert.foley@linaro.org>
---
 cpus.c                | 48 +++++++++++++++++++++++++++++++++++++++++--
 include/hw/core/cpu.h | 33 +++++++++++++++++++++++++++++
 stubs/Makefile.objs   |  1 +
 stubs/cpu-lock.c      | 28 +++++++++++++++++++++++++
 4 files changed, 108 insertions(+), 2 deletions(-)
 create mode 100644 stubs/cpu-lock.c

diff --git a/cpus.c b/cpus.c
index 71bd2f5d55..633734fb5c 100644
--- a/cpus.c
+++ b/cpus.c
@@ -91,6 +91,47 @@ static unsigned int throttle_percentage;
 #define CPU_THROTTLE_PCT_MAX 99
 #define CPU_THROTTLE_TIMESLICE_NS 10000000
 
+/* XXX: is this really the max number of CPUs? */
+#define CPU_LOCK_BITMAP_SIZE 2048
+
+/*
+ * Note: we index the bitmap with cpu->cpu_index + 1 so that the logic
+ * also works during early CPU initialization, when cpu->cpu_index is set to
+ * UNASSIGNED_CPU_INDEX == -1.
+ */
+static __thread DECLARE_BITMAP(cpu_lock_bitmap, CPU_LOCK_BITMAP_SIZE);
+
+bool no_cpu_mutex_locked(void)
+{
+    return bitmap_empty(cpu_lock_bitmap, CPU_LOCK_BITMAP_SIZE);
+}
+
+void cpu_mutex_lock_impl(CPUState *cpu, const char *file, int line)
+{
+/* coverity gets confused by the indirect function call */
+#ifdef __COVERITY__
+    qemu_mutex_lock_impl(&cpu->lock, file, line);
+#else
+    QemuMutexLockFunc f = atomic_read(&qemu_mutex_lock_func);
+
+    g_assert(!cpu_mutex_locked(cpu));
+    set_bit(cpu->cpu_index + 1, cpu_lock_bitmap);
+    f(&cpu->lock, file, line);
+#endif
+}
+
+void cpu_mutex_unlock_impl(CPUState *cpu, const char *file, int line)
+{
+    g_assert(cpu_mutex_locked(cpu));
+    qemu_mutex_unlock_impl(&cpu->lock, file, line);
+    clear_bit(cpu->cpu_index + 1, cpu_lock_bitmap);
+}
+
+bool cpu_mutex_locked(const CPUState *cpu)
+{
+    return test_bit(cpu->cpu_index + 1, cpu_lock_bitmap);
+}
+
 bool cpu_is_stopped(CPUState *cpu)
 {
     return cpu->stopped || !runstate_is_running();
@@ -100,9 +141,9 @@ static inline bool cpu_work_list_empty(CPUState *cpu)
 {
     bool ret;
 
-    qemu_mutex_lock(&cpu->lock);
+    cpu_mutex_lock(cpu);
     ret = QSIMPLEQ_EMPTY(&cpu->work_list);
-    qemu_mutex_unlock(&cpu->lock);
+    cpu_mutex_unlock(cpu);
     return ret;
 }
 
@@ -1837,6 +1878,9 @@ void qemu_mutex_lock_iothread_impl(const char *file, int line)
 {
     QemuMutexLockFunc bql_lock = atomic_read(&qemu_bql_mutex_lock_func);
 
+    /* enforce locking order */
+    g_assert(no_cpu_mutex_locked());
+
     g_assert(!qemu_mutex_iothread_locked());
     bql_lock(&qemu_global_mutex, file, line);
     iothread_locked = true;
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 0b75fdb093..4521bba7a5 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -457,6 +457,39 @@ extern CPUTailQ cpus;
 
 extern __thread CPUState *current_cpu;
 
+/**
+ * cpu_mutex_lock - lock a CPU's mutex
+ * @cpu: the CPU whose mutex is to be locked
+ *
+ * To avoid deadlock, a CPU's mutex must be acquired after the BQL.
+ */
+#define cpu_mutex_lock(cpu)                             \
+    cpu_mutex_lock_impl(cpu, __FILE__, __LINE__)
+void cpu_mutex_lock_impl(CPUState *cpu, const char *file, int line);
+
+/**
+ * cpu_mutex_unlock - unlock a CPU's mutex
+ * @cpu: the CPU whose mutex is to be unlocked
+ */
+#define cpu_mutex_unlock(cpu)                           \
+    cpu_mutex_unlock_impl(cpu, __FILE__, __LINE__)
+void cpu_mutex_unlock_impl(CPUState *cpu, const char *file, int line);
+
+/**
+ * cpu_mutex_locked - check whether a CPU's mutex is locked
+ * @cpu: the CPU of interest
+ *
+ * Returns true if the calling thread is currently holding the CPU's mutex.
+ */
+bool cpu_mutex_locked(const CPUState *cpu);
+
+/**
+ * no_cpu_mutex_locked - check whether any CPU mutex is held
+ *
+ * Returns true if the calling thread is not holding any CPU mutex.
+ */
+bool no_cpu_mutex_locked(void);
+
 static inline void cpu_tb_jmp_cache_clear(CPUState *cpu)
 {
     unsigned int i;
diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
index 45be5dc0ed..d2dd6c94cc 100644
--- a/stubs/Makefile.objs
+++ b/stubs/Makefile.objs
@@ -5,6 +5,7 @@ stub-obj-y += blockdev-close-all-bdrv-states.o
 stub-obj-y += clock-warp.o
 stub-obj-y += cpu-get-clock.o
 stub-obj-y += cpu-get-icount.o
+stub-obj-y += cpu-lock.o
 stub-obj-y += dump.o
 stub-obj-y += error-printf.o
 stub-obj-y += fdset.o
diff --git a/stubs/cpu-lock.c b/stubs/cpu-lock.c
new file mode 100644
index 0000000000..ca2ea8a9c2
--- /dev/null
+++ b/stubs/cpu-lock.c
@@ -0,0 +1,28 @@
+#include "qemu/osdep.h"
+#include "hw/core/cpu.h"
+
+void cpu_mutex_lock_impl(CPUState *cpu, const char *file, int line)
+{
+/* coverity gets confused by the indirect function call */
+#ifdef __COVERITY__
+    qemu_mutex_lock_impl(&cpu->lock, file, line);
+#else
+    QemuMutexLockFunc f = atomic_read(&qemu_mutex_lock_func);
+    f(&cpu->lock, file, line);
+#endif
+}
+
+void cpu_mutex_unlock_impl(CPUState *cpu, const char *file, int line)
+{
+    qemu_mutex_unlock_impl(&cpu->lock, file, line);
+}
+
+bool cpu_mutex_locked(const CPUState *cpu)
+{
+    return true;
+}
+
+bool no_cpu_mutex_locked(void)
+{
+    return true;
+}
-- 
2.17.1



  parent reply index

Thread overview: 100+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-26 19:30 [PATCH v8 00/74] per-CPU locks Robert Foley
2020-03-26 19:30 ` [PATCH v8 01/74] cpu: convert queued work to a QSIMPLEQ Robert Foley
2020-03-26 19:30 ` [PATCH v8 02/74] cpu: rename cpu->work_mutex to cpu->lock Robert Foley
2020-05-11 14:48   ` Alex Bennée
2020-05-11 16:33     ` Robert Foley
2020-03-26 19:30 ` Robert Foley [this message]
2020-05-11 10:24   ` [PATCH v8 03/74] cpu: introduce cpu_mutex_lock/unlock Alex Bennée
2020-05-11 16:09     ` Robert Foley
2020-03-26 19:30 ` [PATCH v8 04/74] cpu: make qemu_work_cond per-cpu Robert Foley
2020-03-26 19:30 ` [PATCH v8 05/74] cpu: move run_on_cpu to cpus-common Robert Foley
2020-03-26 19:30 ` [PATCH v8 06/74] cpu: introduce process_queued_cpu_work_locked Robert Foley
2020-03-26 19:30 ` [PATCH v8 07/74] cpu: make per-CPU locks an alias of the BQL in TCG rr mode Robert Foley
2020-03-26 19:30 ` [PATCH v8 08/74] tcg-runtime: define helper_cpu_halted_set Robert Foley
2020-03-26 19:30 ` [PATCH v8 09/74] ppc: convert to helper_cpu_halted_set Robert Foley
2020-03-26 19:30 ` [PATCH v8 10/74] cris: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 11/74] hppa: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 12/74] m68k: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 13/74] alpha: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 14/74] microblaze: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 15/74] cpu: define cpu_halted helpers Robert Foley
2020-03-26 19:30 ` [PATCH v8 16/74] tcg-runtime: convert to cpu_halted_set Robert Foley
2020-03-26 19:30 ` [PATCH v8 17/74] hw/semihosting: " Robert Foley
2020-05-11 10:25   ` Alex Bennée
2020-03-26 19:31 ` [PATCH v8 18/74] arm: convert to cpu_halted Robert Foley
2020-03-26 19:31 ` [PATCH v8 19/74] ppc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 20/74] sh4: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 21/74] i386: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 22/74] lm32: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 23/74] m68k: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 24/74] mips: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 25/74] riscv: " Robert Foley
2020-05-11 10:40   ` Alex Bennée
2020-05-11 16:13     ` Robert Foley
2020-03-26 19:31 ` [PATCH v8 26/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 27/74] sparc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 28/74] xtensa: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 29/74] gdbstub: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 30/74] openrisc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 31/74] cpu-exec: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 32/74] cpu: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 33/74] cpu: define cpu_interrupt_request helpers Robert Foley
2020-03-26 19:31 ` [PATCH v8 34/74] ppc: use cpu_reset_interrupt Robert Foley
2020-03-26 19:31 ` [PATCH v8 35/74] exec: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 36/74] i386: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 37/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 38/74] openrisc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 39/74] arm: convert to cpu_interrupt_request Robert Foley
2020-03-26 19:31 ` [PATCH v8 40/74] i386: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 41/74] i386/kvm: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 42/74] i386/hax-all: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 43/74] i386/whpx-all: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 44/74] i386/hvf: convert to cpu_request_interrupt Robert Foley
2020-03-26 19:31 ` [PATCH v8 45/74] ppc: convert to cpu_interrupt_request Robert Foley
2020-03-26 19:31 ` [PATCH v8 46/74] sh4: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 47/74] cris: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 48/74] hppa: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 49/74] lm32: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 50/74] m68k: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 51/74] mips: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 52/74] nios: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 53/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 54/74] alpha: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 55/74] moxie: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 56/74] sparc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 57/74] openrisc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 58/74] unicore32: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 59/74] microblaze: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 60/74] accel/tcg: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 61/74] cpu: convert to interrupt_request Robert Foley
2020-03-26 19:31 ` [PATCH v8 62/74] cpu: call .cpu_has_work with the CPU lock held Robert Foley
2020-03-26 19:31 ` [PATCH v8 63/74] cpu: introduce cpu_has_work_with_iothread_lock Robert Foley
2020-03-26 19:31 ` [PATCH v8 64/74] ppc: convert to cpu_has_work_with_iothread_lock Robert Foley
2020-03-26 19:31 ` [PATCH v8 65/74] mips: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 66/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 67/74] riscv: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 68/74] sparc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 69/74] xtensa: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 70/74] cpu: rename all_cpu_threads_idle to qemu_tcg_rr_all_cpu_threads_idle Robert Foley
2020-03-26 19:31 ` [PATCH v8 71/74] cpu: protect CPU state with cpu->lock instead of the BQL Robert Foley
2020-03-26 19:31 ` [PATCH v8 72/74] cpus-common: release BQL earlier in run_on_cpu Robert Foley
2020-03-26 19:31 ` [PATCH v8 73/74] cpu: add async_run_on_cpu_no_bql Robert Foley
2020-03-26 19:31 ` [PATCH v8 74/74] cputlb: queue async flush jobs without the BQL Robert Foley
2020-05-12 16:27   ` Alex Bennée
2020-05-12 19:26     ` Robert Foley
2020-05-18 13:46       ` Robert Foley
2020-05-20  4:46         ` Emilio G. Cota
2020-05-20 15:01           ` Robert Foley
2020-05-21 14:17             ` Robert Foley
2020-05-12 18:38   ` Alex Bennée
2020-03-26 22:58 ` [PATCH v8 00/74] per-CPU locks Aleksandar Markovic
2020-03-27  9:39   ` Alex Bennée
2020-03-27  9:50     ` Aleksandar Markovic
2020-03-27 10:24       ` Aleksandar Markovic
2020-03-27 17:21         ` Robert Foley
2020-03-27  5:14 ` Emilio G. Cota
2020-03-27 10:59   ` Philippe Mathieu-Daudé
2020-03-30  8:57     ` Stefan Hajnoczi
2020-03-27 18:23   ` Alex Bennée
2020-03-27 18:30   ` Robert Foley
2020-05-12 16:29 ` Alex Bennée

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