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new 0.1.5 | Oct 18, 2024 |
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0.1.4 | Aug 11, 2024 |
0.1.3 | Jul 26, 2024 |
#1646 in Procedural macros
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Used in percpu
23KB
335 lines
percpu
Define and access per-CPU data structures.
All per-CPU data is placed into several contiguous memory regions called
per-CPU data areas, the number of which is the number of CPUs. Each CPU
has its own per-CPU data area. The architecture-specific thread pointer
register (e.g., GS_BASE
on x86_64) is set to the base address of the area
on initialization.
When accessing the per-CPU data on the current CPU, it first use the thread pointer register to obtain the corresponding per-CPU data area, and then add an offset to access the corresponding field.
Examples
#[percpu::def_percpu]
static CPU_ID: usize = 0;
// initialize per-CPU data for 4 CPUs.
percpu::init(4);
// set the thread pointer register to the per-CPU data area 0.
percpu::set_local_thread_pointer(0);
// access the per-CPU data `CPU_ID` on the current CPU.
println!("{}", CPU_ID.read_current()); // prints "0"
CPU_ID.write_current(1);
println!("{}", CPU_ID.read_current()); // prints "1"
Currently, you need to modify the linker script manually, add the following lines to your linker script:
. = ALIGN(4K);
_percpu_start = .;
.percpu 0x0 (NOLOAD) : AT(_percpu_start) {
_percpu_load_start = .;
*(.percpu .percpu.*)
_percpu_load_end = .;
. = _percpu_load_start + ALIGN(64) * CPU_NUM;
}
. = _percpu_start + SIZEOF(.percpu);
Cargo Features
sp-naive
: For single-core use. In this case, each per-CPU data is just a global variable, architecture-specific thread pointer register is not used.preempt
: For preemptible system use. In this case, we need to disable preemption when accessing per-CPU data. Otherwise, the data may be corrupted when it's being accessing and the current thread happens to be preempted.arm-el2
: For ARM system running at EL2 use (e.g. hypervisors). In this case, we useTPIDR_EL2
instead ofTPIDR_EL1
to store the base address of per-CPU data area.
Note for RISC-V
Since RISC-V does not provide separate thread pointer registers for user and
kernel mode, we temporarily use the gp
register to point to the per-CPU data
area, while the tp
register is used for thread-local storage.
Dependencies
~300–760KB
~18K SLoC