diff options
| author | Anup Patel <anup.patel@wdc.com> | 2020-08-15 19:41:11 +0530 |
|---|---|---|
| committer | Anup Patel <anup@brainfault.org> | 2020-08-21 19:35:28 +0530 |
| commit | e435ba05248a10a5085858c46fe11854373d5dbc (patch) | |
| tree | 9f70db842f269c701ef3b8286186ab48ead6705c /lib/sbi/sbi_init.c | |
| parent | d7f87d99a33b71b20af527c62e7ef95dcb61ee22 (diff) | |
lib: sbi_init: Avoid thundering hurd problem with coldboot_lock
We can have thundering hurd problem with coldboot_lock where the
boot HART can potentially starve trying to acquire coldboot_lock
because some of the non-boot HARTs are continuously acquiring and
releasing coldboot_lock. This can happen if MIP.MSIP bit is already
set for some of the non-boot HARTs.
To avoid thundering hurd problem for coldboot_lock, we use the
__smp_load_acquire() and __smp_store_release() for coldboot_done
flag and use coldboot_lock only for coldboot_wait_hmask.
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Diffstat (limited to 'lib/sbi/sbi_init.c')
| -rw-r--r-- | lib/sbi/sbi_init.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c index a7fb848..c438eaa 100644 --- a/lib/sbi/sbi_init.c +++ b/lib/sbi/sbi_init.c @@ -9,6 +9,7 @@ #include <sbi/riscv_asm.h> #include <sbi/riscv_atomic.h> +#include <sbi/riscv_barrier.h> #include <sbi/riscv_locks.h> #include <sbi/sbi_console.h> #include <sbi/sbi_ecall.h> @@ -85,9 +86,10 @@ static void sbi_boot_prints(struct sbi_scratch *scratch, u32 hartid) } static spinlock_t coldboot_lock = SPIN_LOCK_INITIALIZER; -static unsigned long coldboot_done = 0; static struct sbi_hartmask coldboot_wait_hmask = { 0 }; +static unsigned long coldboot_done; + static void wait_for_coldboot(struct sbi_scratch *scratch, u32 hartid) { unsigned long saved_mie, cmip; @@ -105,16 +107,20 @@ static void wait_for_coldboot(struct sbi_scratch *scratch, u32 hartid) /* Mark current HART as waiting */ sbi_hartmask_set_hart(hartid, &coldboot_wait_hmask); + /* Release coldboot lock */ + spin_unlock(&coldboot_lock); + /* Wait for coldboot to finish using WFI */ - while (!coldboot_done) { - spin_unlock(&coldboot_lock); + while (!__smp_load_acquire(&coldboot_done)) { do { wfi(); cmip = csr_read(CSR_MIP); } while (!(cmip & MIP_MSIP)); - spin_lock(&coldboot_lock); }; + /* Acquire coldboot lock */ + spin_lock(&coldboot_lock); + /* Unmark current HART as waiting */ sbi_hartmask_clear_hart(hartid, &coldboot_wait_hmask); @@ -132,12 +138,12 @@ static void wake_coldboot_harts(struct sbi_scratch *scratch, u32 hartid) { const struct sbi_platform *plat = sbi_platform_ptr(scratch); + /* Mark coldboot done */ + __smp_store_release(&coldboot_done, 1); + /* Acquire coldboot lock */ spin_lock(&coldboot_lock); - /* Mark coldboot done */ - coldboot_done = 1; - /* Send an IPI to all HARTs waiting for coldboot */ for (int i = 0; i <= sbi_scratch_last_hartid(); i++) { if ((i != hartid) && |