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 <paul...@linux.vnet.ibm.com>
Signed-off-by: Li Zhong <zh...@linux.vnet.ibm.com>
Tested-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
---
arch/powerpc/platforms/pseries/hvCall_inst.c | 4 +---
arch/powerpc/platforms/pseries/lpar.c | 2 ++
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/hvCall_inst.c
b/arch/powerpc/platforms/pseries/hvCall_inst.c
index f106662..c9311cf 100644
--- 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 *ignored, unsigned long
opcode, unsigned long
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 *ignored, unsigned long
opcode, unsigned long
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)
diff --git a/arch/powerpc/platforms/pseries/lpar.c
b/arch/powerpc/platforms/pseries/lpar.c
index 27a4950..dc36ea6 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -554,6 +554,7 @@ void __trace_hcall_entry(unsigned long opcode, unsigned
long *args)
goto out;
(*depth)++;
+ preempt_disable();
trace_hcall_entry(opcode, args);
(*depth)--;
@@ -576,6 +577,7 @@ void __trace_hcall_exit(long opcode, unsigned long retval,
(*depth)++;
trace_hcall_exit(opcode, retval, retbuf);
+ preempt_enable();
(*depth)--;
out:
--
1.7.5.4
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