| From e4f387d8db3ba3c2dae4d8bdfe7bb5f4fe1bcb0d Mon Sep 17 00:00:00 2001 |
| From: Li Zhong <zhong@linux.vnet.ibm.com> |
| Date: Sun, 18 Dec 2011 16:03:04 +0000 |
| Subject: powerpc: Fix unpaired probe_hcall_entry and probe_hcall_exit |
| |
| From: Li Zhong <zhong@linux.vnet.ibm.com> |
| |
| commit e4f387d8db3ba3c2dae4d8bdfe7bb5f4fe1bcb0d upstream. |
| |
| Unpaired calling of probe_hcall_entry and probe_hcall_exit might happen |
| as following, which could cause incorrect preempt count. |
| |
| __trace_hcall_entry => trace_hcall_entry -> probe_hcall_entry => |
| get_cpu_var => preempt_disable |
| |
| __trace_hcall_exit => trace_hcall_exit -> probe_hcall_exit => |
| put_cpu_var => preempt_enable |
| |
| where: |
| A => B and A -> B means A calls B, but |
| => means A will call B through function name, and B will definitely be |
| called. |
| -> means A will call B through function pointer, so B might not be |
| called if the function pointer is not set. |
| |
| So error happens when only one of probe_hcall_entry and probe_hcall_exit |
| get called during a hcall. |
| |
| This patch tries to move the preempt count operations from |
| probe_hcall_entry and probe_hcall_exit to its callers. |
| |
| Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com> |
| Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| |
| --- |
| arch/powerpc/platforms/pseries/hvCall_inst.c | 4 +--- |
| arch/powerpc/platforms/pseries/lpar.c | 2 ++ |
| 2 files changed, 3 insertions(+), 3 deletions(-) |
| |
| --- a/arch/powerpc/platforms/pseries/hvCall_inst.c |
| +++ b/arch/powerpc/platforms/pseries/hvCall_inst.c |
| @@ -109,7 +109,7 @@ static void probe_hcall_entry(void *igno |
| if (opcode > MAX_HCALL_OPCODE) |
| return; |
| |
| - h = &get_cpu_var(hcall_stats)[opcode / 4]; |
| + h = &__get_cpu_var(hcall_stats)[opcode / 4]; |
| h->tb_start = mftb(); |
| h->purr_start = mfspr(SPRN_PURR); |
| } |
| @@ -126,8 +126,6 @@ static void probe_hcall_exit(void *ignor |
| h->num_calls++; |
| h->tb_total += mftb() - h->tb_start; |
| h->purr_total += mfspr(SPRN_PURR) - h->purr_start; |
| - |
| - put_cpu_var(hcall_stats); |
| } |
| |
| static int __init hcall_inst_init(void) |
| --- a/arch/powerpc/platforms/pseries/lpar.c |
| +++ b/arch/powerpc/platforms/pseries/lpar.c |
| @@ -554,6 +554,7 @@ void __trace_hcall_entry(unsigned long o |
| goto out; |
| |
| (*depth)++; |
| + preempt_disable(); |
| trace_hcall_entry(opcode, args); |
| (*depth)--; |
| |
| @@ -576,6 +577,7 @@ void __trace_hcall_exit(long opcode, uns |
| |
| (*depth)++; |
| trace_hcall_exit(opcode, retval, retbuf); |
| + preempt_enable(); |
| (*depth)--; |
| |
| out: |