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Commit e4f387d8 authored by Li Zhong's avatar Li Zhong Committed by Benjamin Herrenschmidt
Browse files

powerpc: Fix unpaired probe_hcall_entry and probe_hcall_exit 



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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarLi Zhong <zhong@linux.vnet.ibm.com>
Tested-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
CC: stable@kernel.org [v2.6.32+]
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 1bb0b7d2

arch/powerpc/platforms/pseries/hvCall_inst.c

+1 −3
Original line number Diff line number Diff line
@@ -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)

arch/powerpc/platforms/pseries/lpar.c

+2 −0
Original line number Diff line number Diff line
@@ -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: