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powerpc: Fix unpaired probe_hcall_entry and probe_hcall_exit

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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>
This commit is contained in:
Li Zhong 2011-12-18 16:03:04 +00:00 committed by Greg Kroah-Hartman
parent 4df2f43452
commit 1e858f50ca
2 changed files with 3 additions and 3 deletions
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4
arch/powerpc/platforms/pseries/hvCall_inst.c
View File

@ -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)

2
arch/powerpc/platforms/pseries/lpar.c
View File

@ -553,6 +553,7 @@ void __trace_hcall_entry(unsigned long opcode, unsigned long *args)
goto out;
(*depth)++;
preempt_disable();
trace_hcall_entry(opcode, args);
(*depth)--;
@ -575,6 +576,7 @@ void __trace_hcall_exit(long opcode, unsigned long retval,
(*depth)++;
trace_hcall_exit(opcode, retval, retbuf);
preempt_enable();
(*depth)--;
out: