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accel: use atomic accesses for exit_request

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CPU threads write exit_request as a "note to self" that they need to
go out to a slow path.  This write happens out of the BQL and can be
a data race with another threads' cpu_exit(); use atomic accesses
consistently.

While at it, change the source argument from int ("1") to bool ("true").

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2025-08-08 18:55:48 +02:00
parent ac6c8a390b
commit f084ff128b
9 changed files with 24 additions and 15 deletions
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9
include/hw/core/cpu.h
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@ -422,6 +422,15 @@ struct qemu_work_item;
* valid under cpu_list_lock.
* @created: Indicates whether the CPU thread has been successfully created.
* @halt_cond: condition variable sleeping threads can wait on.
* @exit_request: Another thread requests the CPU to call qemu_wait_io_event().
* Should be read only by CPU thread with load-acquire, to synchronize with
* other threads' store-release operation.
*
* In some cases, accelerator-specific code will write exit_request from
* within the same thread, to "bump" the effect of qemu_cpu_kick() to
* the one provided by cpu_exit(), especially when processing interrupt
* flags. In this case, the write and read happen in the same thread
* and the write therefore can use qemu_atomic_set().
* @interrupt_request: Indicates a pending interrupt request.
* Only used by system emulation.
* @halted: Nonzero if the CPU is in suspended state.