blob: 8cb1419d72aedb1ca0b5bb902cdb431de733199b [file] [log] [blame]
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: