| From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 55/55] powerpc: Work around tracing from dyntick-idle mode | Date | Tue, 6 Sep 2011 11:00:49 -0700 |
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PowerPC LPAR's __trace_hcall_exit() can invoke event tracing at a point where RCU has been told that the CPU is in dyntick-idle mode. Because event tracing uses RCU, this can result in failures.
A correct fix would arrange for RCU to be told about dyntick-idle mode after tracing had completed, however, this will require some care because it appears that __trace_hcall_exit() can also be called from non-dyntick-idle mode.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: anton@samba.org Cc: benh@kernel.crashing.org Cc: paulus@samba.org --- arch/powerpc/platforms/pseries/lpar.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 39e6e0a..668f300 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -715,12 +715,14 @@ EXPORT_SYMBOL(arch_free_page); /* NB: reg/unreg are called while guarded with the tracepoints_mutex */ extern long hcall_tracepoint_refcount; +#if 0 /* work around buggy use of RCU from dyntick-idle mode */ /* * Since the tracing code might execute hcalls we need to guard against * recursion. One example of this are spinlocks calling H_YIELD on * shared processor partitions. */ static DEFINE_PER_CPU(unsigned int, hcall_trace_depth); +#endif /* #if 0 work around buggy use of RCU from dyntick-idle mode */ void hcall_tracepoint_regfunc(void) { @@ -734,6 +736,7 @@ void hcall_tracepoint_unregfunc(void) void __trace_hcall_entry(unsigned long opcode, unsigned long *args) { +#if 0 /* work around buggy use of RCU from dyntick-idle mode */ unsigned long flags; unsigned int *depth; @@ -750,11 +753,13 @@ void __trace_hcall_entry(unsigned long opcode, unsigned long *args) out: local_irq_restore(flags); +#endif /* #if 0 work around buggy use of RCU from dyntick-idle mode */ } void __trace_hcall_exit(long opcode, unsigned long retval, unsigned long *retbuf) { +#if 0 /* work around buggy use of RCU from dyntick-idle mode */ unsigned long flags; unsigned int *depth; @@ -771,6 +776,7 @@ void __trace_hcall_exit(long opcode, unsigned long retval, out: local_irq_restore(flags); +#endif /* #if 0 work around buggy use of RCU from dyntick-idle mode */ } #endif -- 1.7.3.2
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