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Diffstat (limited to 'arch/powerpc/include/asm/paravirt.h')
-rw-r--r--arch/powerpc/include/asm/paravirt.h22
1 files changed, 19 insertions, 3 deletions
diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h
index 5d1726bb28e7..bcb7b5f917be 100644
--- a/arch/powerpc/include/asm/paravirt.h
+++ b/arch/powerpc/include/asm/paravirt.h
@@ -28,19 +28,35 @@ static inline u32 yield_count_of(int cpu)
return be32_to_cpu(yield_count);
}
+/*
+ * Spinlock code confers and prods, so don't trace the hcalls because the
+ * tracing code takes spinlocks which can cause recursion deadlocks.
+ *
+ * These calls are made while the lock is not held: the lock slowpath yields if
+ * it can not acquire the lock, and unlock slow path might prod if a waiter has
+ * yielded). So this may not be a problem for simple spin locks because the
+ * tracing does not technically recurse on the lock, but we avoid it anyway.
+ *
+ * However the queued spin lock contended path is more strictly ordered: the
+ * H_CONFER hcall is made after the task has queued itself on the lock, so then
+ * recursing on that lock will cause the task to then queue up again behind the
+ * first instance (or worse: queued spinlocks use tricks that assume a context
+ * never waits on more than one spinlock, so such recursion may cause random
+ * corruption in the lock code).
+ */
static inline void yield_to_preempted(int cpu, u32 yield_count)
{
- plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(cpu), yield_count);
+ plpar_hcall_norets_notrace(H_CONFER, get_hard_smp_processor_id(cpu), yield_count);
}
static inline void prod_cpu(int cpu)
{
- plpar_hcall_norets(H_PROD, get_hard_smp_processor_id(cpu));
+ plpar_hcall_norets_notrace(H_PROD, get_hard_smp_processor_id(cpu));
}
static inline void yield_to_any(void)
{
- plpar_hcall_norets(H_CONFER, -1, 0);
+ plpar_hcall_norets_notrace(H_CONFER, -1, 0);
}
#else
static inline bool is_shared_processor(void)