[PATCH v5 27/33] riscv: Fix race conditions when initializing IPI
Rick Chen
rickchen36 at gmail.com
Mon Mar 2 10:08:02 CET 2020
Hi Sean
> The IPI code could have race conditions in several places.
> * Several harts could race on the value of gd->arch->clint/plic
> * Non-boot harts could race with the main hart on the DM subsystem In
> addition, if an IPI was pending when U-Boot started, it would cause the
> IPI handler to jump to address 0.
>
> To address these problems, a new function riscv_init_ipi is introduced. It
> is called once during arch_cpu_init_dm. Before this point, no riscv_*_ipi
> functions may be called. Access is synchronized by gd->arch->ipi_ready.
>
> Signed-off-by: Sean Anderson <seanga2 at gmail.com>
> ---
>
> Changes in v5:
> - New
>
> arch/riscv/cpu/cpu.c | 9 ++++
> arch/riscv/include/asm/global_data.h | 1 +
> arch/riscv/include/asm/smp.h | 43 ++++++++++++++++++
> arch/riscv/lib/andes_plic.c | 34 +++++---------
> arch/riscv/lib/sbi_ipi.c | 5 ++
> arch/riscv/lib/sifive_clint.c | 33 +++++---------
> arch/riscv/lib/smp.c | 68 ++++++++--------------------
> 7 files changed, 101 insertions(+), 92 deletions(-)
>
> diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
> index e457f6acbf..a971ec8694 100644
> --- a/arch/riscv/cpu/cpu.c
> +++ b/arch/riscv/cpu/cpu.c
> @@ -96,6 +96,15 @@ int arch_cpu_init_dm(void)
> csr_write(CSR_SATP, 0);
> }
>
> +#ifdef CONFIG_SMP
> + ret = riscv_init_ipi();
> + if (ret)
> + return ret;
> +
> + /* Atomically set a flag enabling IPI handling */
> + WRITE_ONCE(gd->arch.ipi_ready, 1);
I think it shall not have race condition here.
Can you explain more detail why there will occur race condition ?
Hi Lukas
Do you have any comments ?
Thanks
Rick
> +#endif
> +
> return 0;
> }
>
> diff --git a/arch/riscv/include/asm/global_data.h b/arch/riscv/include/asm/global_data.h
> index 7276d9763f..b24f8fd2a7 100644
> --- a/arch/riscv/include/asm/global_data.h
> +++ b/arch/riscv/include/asm/global_data.h
> @@ -28,6 +28,7 @@ struct arch_global_data {
> #endif
> #ifdef CONFIG_SMP
> struct ipi_data ipi[CONFIG_NR_CPUS];
> + long ipi_ready; /* Set after riscv_init_ipi is called */
> #endif
> #ifndef CONFIG_XIP
> ulong available_harts;
> diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
> index 74de92ed13..1b428856b2 100644
> --- a/arch/riscv/include/asm/smp.h
> +++ b/arch/riscv/include/asm/smp.h
> @@ -51,4 +51,47 @@ void handle_ipi(ulong hart);
> */
> int smp_call_function(ulong addr, ulong arg0, ulong arg1, int wait);
>
> +/**
> + * riscv_init_ipi() - Initialize inter-process interrupt (IPI) driver
> + *
> + * Platform code must provide this function. This function is called once after
> + * the cpu driver is initialized. No other riscv_*_ipi() calls will be made
> + * before this function is called.
> + *
> + * @return 0 if OK, -ve on error
> + */
> +int riscv_init_ipi(void);
> +
> +/**
> + * riscv_send_ipi() - Send inter-processor interrupt (IPI)
> + *
> + * Platform code must provide this function.
> + *
> + * @hart: Hart ID of receiving hart
> + * @return 0 if OK, -ve on error
> + */
> +int riscv_send_ipi(int hart);
> +
> +/**
> + * riscv_clear_ipi() - Clear inter-processor interrupt (IPI)
> + *
> + * Platform code must provide this function.
> + *
> + * @hart: Hart ID of hart to be cleared
> + * @return 0 if OK, -ve on error
> + */
> +int riscv_clear_ipi(int hart);
> +
> +/**
> + * riscv_get_ipi() - Get status of inter-processor interrupt (IPI)
> + *
> + * Platform code must provide this function.
> + *
> + * @hart: Hart ID of hart to be checked
> + * @pending: Pointer to variable with result of the check,
> + * 1 if IPI is pending, 0 otherwise
> + * @return 0 if OK, -ve on error
> + */
> +int riscv_get_ipi(int hart, int *pending);
> +
> #endif
> diff --git a/arch/riscv/lib/andes_plic.c b/arch/riscv/lib/andes_plic.c
> index 20529ab3eb..8484f76386 100644
> --- a/arch/riscv/lib/andes_plic.c
> +++ b/arch/riscv/lib/andes_plic.c
> @@ -30,20 +30,6 @@
> #define SEND_IPI_TO_HART(hart) (0x80 >> (hart))
>
> DECLARE_GLOBAL_DATA_PTR;
> -static int init_plic(void);
> -
> -#define PLIC_BASE_GET(void) \
> - do { \
> - long *ret; \
> - \
> - if (!gd->arch.plic) { \
> - ret = syscon_get_first_range(RISCV_SYSCON_PLIC); \
> - if (IS_ERR(ret)) \
> - return PTR_ERR(ret); \
> - gd->arch.plic = ret; \
> - init_plic(); \
> - } \
> - } while (0)
>
> static int enable_ipi(int hart)
> {
> @@ -93,13 +79,21 @@ static int init_plic(void)
> return -ENODEV;
> }
>
> +int riscv_init_ipi(void)
> +{
> + int ret = syscon_get_first_range(RISCV_SYSCON_PLIC);
> +
> + if (IS_ERR(ret))
> + return PTR_ERR(ret);
> + gd->arch.plic = ret;
> +
> + return init_plic();
> +}
> +
> int riscv_send_ipi(int hart)
> {
> - unsigned int ipi;
> + unsigned int ipi = (SEND_IPI_TO_HART(hart) << (8 * gd->arch.boot_hart));
>
> - PLIC_BASE_GET();
> -
> - ipi = (SEND_IPI_TO_HART(hart) << (8 * gd->arch.boot_hart));
> writel(ipi, (void __iomem *)PENDING_REG(gd->arch.plic,
> gd->arch.boot_hart));
>
> @@ -110,8 +104,6 @@ int riscv_clear_ipi(int hart)
> {
> u32 source_id;
>
> - PLIC_BASE_GET();
> -
> source_id = readl((void __iomem *)CLAIM_REG(gd->arch.plic, hart));
> writel(source_id, (void __iomem *)CLAIM_REG(gd->arch.plic, hart));
>
> @@ -120,8 +112,6 @@ int riscv_clear_ipi(int hart)
>
> int riscv_get_ipi(int hart, int *pending)
> {
> - PLIC_BASE_GET();
> -
> *pending = readl((void __iomem *)PENDING_REG(gd->arch.plic,
> gd->arch.boot_hart));
> *pending = !!(*pending & SEND_IPI_TO_HART(hart));
> diff --git a/arch/riscv/lib/sbi_ipi.c b/arch/riscv/lib/sbi_ipi.c
> index 9a698ce74e..310d1bd2a4 100644
> --- a/arch/riscv/lib/sbi_ipi.c
> +++ b/arch/riscv/lib/sbi_ipi.c
> @@ -7,6 +7,11 @@
> #include <common.h>
> #include <asm/sbi.h>
>
> +int riscv_init_ipi(void)
> +{
> + return 0;
> +}
> +
> int riscv_send_ipi(int hart)
> {
> ulong mask;
> diff --git a/arch/riscv/lib/sifive_clint.c b/arch/riscv/lib/sifive_clint.c
> index 5e0d25720b..62c1b2b0ef 100644
> --- a/arch/riscv/lib/sifive_clint.c
> +++ b/arch/riscv/lib/sifive_clint.c
> @@ -24,22 +24,8 @@
>
> DECLARE_GLOBAL_DATA_PTR;
>
> -#define CLINT_BASE_GET(void) \
> - do { \
> - long *ret; \
> - \
> - if (!gd->arch.clint) { \
> - ret = syscon_get_first_range(RISCV_SYSCON_CLINT); \
> - if (IS_ERR(ret)) \
> - return PTR_ERR(ret); \
> - gd->arch.clint = ret; \
> - } \
> - } while (0)
> -
> int riscv_get_time(u64 *time)
> {
> - CLINT_BASE_GET();
> -
> *time = readq((void __iomem *)MTIME_REG(gd->arch.clint));
>
> return 0;
> @@ -47,17 +33,24 @@ int riscv_get_time(u64 *time)
>
> int riscv_set_timecmp(int hart, u64 cmp)
> {
> - CLINT_BASE_GET();
> -
> writeq(cmp, (void __iomem *)MTIMECMP_REG(gd->arch.clint, hart));
>
> return 0;
> }
>
> +int riscv_init_ipi(void)
> +{
> + long *ret = syscon_get_first_range(RISCV_SYSCON_CLINT);
> +
> + if (IS_ERR(ret))
> + return PTR_ERR(ret);
> + gd->arch.clint = ret;
> +
> + return 0;
> +}
> +
> int riscv_send_ipi(int hart)
> {
> - CLINT_BASE_GET();
> -
> writel(1, (void __iomem *)MSIP_REG(gd->arch.clint, hart));
>
> return 0;
> @@ -65,8 +58,6 @@ int riscv_send_ipi(int hart)
>
> int riscv_clear_ipi(int hart)
> {
> - CLINT_BASE_GET();
> -
> writel(0, (void __iomem *)MSIP_REG(gd->arch.clint, hart));
>
> return 0;
> @@ -74,8 +65,6 @@ int riscv_clear_ipi(int hart)
>
> int riscv_get_ipi(int hart, int *pending)
> {
> - CLINT_BASE_GET();
> -
> *pending = readl((void __iomem *)MSIP_REG(gd->arch.clint, hart));
>
> return 0;
> diff --git a/arch/riscv/lib/smp.c b/arch/riscv/lib/smp.c
> index 17adb35730..3b1e52e9b2 100644
> --- a/arch/riscv/lib/smp.c
> +++ b/arch/riscv/lib/smp.c
> @@ -12,38 +12,6 @@
>
> DECLARE_GLOBAL_DATA_PTR;
>
> -/**
> - * riscv_send_ipi() - Send inter-processor interrupt (IPI)
> - *
> - * Platform code must provide this function.
> - *
> - * @hart: Hart ID of receiving hart
> - * @return 0 if OK, -ve on error
> - */
> -extern int riscv_send_ipi(int hart);
> -
> -/**
> - * riscv_clear_ipi() - Clear inter-processor interrupt (IPI)
> - *
> - * Platform code must provide this function.
> - *
> - * @hart: Hart ID of hart to be cleared
> - * @return 0 if OK, -ve on error
> - */
> -extern int riscv_clear_ipi(int hart);
> -
> -/**
> - * riscv_get_ipi() - Get status of inter-processor interrupt (IPI)
> - *
> - * Platform code must provide this function.
> - *
> - * @hart: Hart ID of hart to be checked
> - * @pending: Pointer to variable with result of the check,
> - * 1 if IPI is pending, 0 otherwise
> - * @return 0 if OK, -ve on error
> - */
> -extern int riscv_get_ipi(int hart, int *pending);
> -
> static int send_ipi_many(struct ipi_data *ipi, int wait)
> {
> ofnode node, cpus;
> @@ -110,37 +78,41 @@ void handle_ipi(ulong hart)
> int ret;
> void (*smp_function)(ulong hart, ulong arg0, ulong arg1);
>
> - if (hart >= CONFIG_NR_CPUS)
> + if (hart >= CONFIG_NR_CPUS || !READ_ONCE(gd->arch.ipi_ready))
> return;
>
> - __smp_mb();
> -
> - smp_function = (void (*)(ulong, ulong, ulong))gd->arch.ipi[hart].addr;
> - invalidate_icache_all();
> -
> /*
> * Clear the IPI to acknowledge the request before jumping to the
> * requested function.
> */
> ret = riscv_clear_ipi(hart);
> if (ret) {
> - pr_err("Cannot clear IPI of hart %ld\n", hart);
> + pr_err("Cannot clear IPI of hart %ld (error %d)\n", hart, ret);
> return;
> }
>
> + __smp_mb();
> +
> + smp_function = (void (*)(ulong, ulong, ulong))gd->arch.ipi[hart].addr;
> + /*
> + * There may be an IPI raised before u-boot begins execution, so check
> + * to ensure we actually have a function to call.
> + */
> + if (!smp_function)
> + return;
> + log_debug("hart = %lu func = %p\n", hart, smp_function);
> + invalidate_icache_all();
> +
> smp_function(hart, gd->arch.ipi[hart].arg0, gd->arch.ipi[hart].arg1);
> }
>
> int smp_call_function(ulong addr, ulong arg0, ulong arg1, int wait)
> {
> - int ret = 0;
> - struct ipi_data ipi;
> + struct ipi_data ipi = {
> + .addr = addr,
> + .arg0 = arg0,
> + .arg1 = arg1,
> + };
>
> - ipi.addr = addr;
> - ipi.arg0 = arg0;
> - ipi.arg1 = arg1;
> -
> - ret = send_ipi_many(&ipi, wait);
> -
> - return ret;
> + return send_ipi_many(&ipi, wait);
> }
> --
> 2.25.0
>
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