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authorNicholas Piggin <npiggin@gmail.com>2017-08-09 22:41:21 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2017-08-09 23:45:26 +1000
commit0459ddfdb31e7d812b555a2530ecbacdf96961a6 (patch)
tree872d7e7c3ea27de89c18a2710c672038281f2c8e /arch
parent7310d5c8c55e8987a854507f71022f8de676bbf4 (diff)
downloadlinux-0459ddfdb31e7d812b555a2530ecbacdf96961a6.tar.bz2
powerpc: NMI IPI improve lock primitive
When the NMI IPI lock is contended, spin at low SMT priority, using loads only, and with interrupts enabled (where possible). This improves behaviour under high contention (e.g., a system crash when a number of CPUs are trying to enter the debugger). Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/kernel/smp.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index cf0e1245b8cc..8d3320562c70 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -351,7 +351,7 @@ static void nmi_ipi_lock_start(unsigned long *flags)
hard_irq_disable();
while (atomic_cmpxchg(&__nmi_ipi_lock, 0, 1) == 1) {
raw_local_irq_restore(*flags);
- cpu_relax();
+ spin_until_cond(atomic_read(&__nmi_ipi_lock) == 0);
raw_local_irq_save(*flags);
hard_irq_disable();
}
@@ -360,7 +360,7 @@ static void nmi_ipi_lock_start(unsigned long *flags)
static void nmi_ipi_lock(void)
{
while (atomic_cmpxchg(&__nmi_ipi_lock, 0, 1) == 1)
- cpu_relax();
+ spin_until_cond(atomic_read(&__nmi_ipi_lock) == 0);
}
static void nmi_ipi_unlock(void)
@@ -475,7 +475,7 @@ int smp_send_nmi_ipi(int cpu, void (*fn)(struct pt_regs *), u64 delay_us)
nmi_ipi_lock_start(&flags);
while (nmi_ipi_busy_count) {
nmi_ipi_unlock_end(&flags);
- cpu_relax();
+ spin_until_cond(nmi_ipi_busy_count == 0);
nmi_ipi_lock_start(&flags);
}