Messages in this thread Patch in this message | | | Date | Tue, 10 Jan 2012 13:45:23 -0800 | From | Greg KH <> | Subject | [10/40] powerpc: Fix unpaired probe_hcall_entry and probe_hcall_exit |
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3.0-stable review patch. If anyone has any objections, please let me know.
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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 @@ -745,6 +745,7 @@ void __trace_hcall_entry(unsigned long o goto out; (*depth)++; + preempt_disable(); trace_hcall_entry(opcode, args); (*depth)--; @@ -767,6 +768,7 @@ void __trace_hcall_exit(long opcode, uns (*depth)++; trace_hcall_exit(opcode, retval, retbuf); + preempt_enable(); (*depth)--; out:
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