linux-kernel - RE: [PATCH v1] perf callchain: fix kernel symbol resolution by remembering the cpumode

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Date:	Fri, 27 Mar 2015 16:09:33 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"paulus@...ba.org" <paulus@...ba.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"acme@...nel.org" <acme@...nel.org>,
	"acme@...hat.com" <acme@...hat.com>,
	"jolsa@...nel.org" <jolsa@...nel.org>,
	"namhyung@...nel.org" <namhyung@...nel.org>,
	"Hunter, Adrian" <adrian.hunter@...el.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"brueckner@...ux.vnet.ibm.com" <brueckner@...ux.vnet.ibm.com>,
	"schwidefsky@...ibm.com" <schwidefsky@...ibm.com>
Subject: RE: [PATCH v1] perf callchain: fix kernel symbol resolution by
 remembering the cpumode



> Commit 2e77784bb7d8 ("perf callchain: Move cpumode resolve code to
> add_callchain_ip") promised "No change in behavior.".
> 
> As this commit breaks callchains on s390x (symbols not getting resolved,
> observed when profiling the kernel), this statement is wrong. The
> cpumode must be kept when iterating over all ips, otherwise the default
> (PERF_RECORD_MISC_USER) will be used by error.

Indeed.
Besides thread__resolve_callchain_sample, lbr path also need to 
be patched.

@@ -1538,6 +1536,7 @@ static int resolve_lbr_callchain_sample
(struct thread *thread,
 {
        struct ip_callchain *chain = sample->callchain;
        int chain_nr = min(max_stack, (int)chain->nr);
+       u8 cpumode = PERF_RECORD_MISC_USER;
        int i, j, err;
        u64 ip;

@@ -1584,7 +1583,7 @@ static int resolve_lbr_callchain_sample
(struct thread *thread,
                                        ip = lbr_stack->entries[0].to;
                        }

-                       err = add_callchain_ip(thread, parent, root_al, false, ip);
+                      err = add_callchain_ip(thread, parent, root_al, &cpumode, ip);
                        if (err)
                                return (err < 0) ? err : 0;
                }

Thanks,
Kan

> 
> Signed-off-by: David Hildenbrand <dahi@...ux.vnet.ibm.com>
> ---
>  tools/perf/util/machine.c | 25 ++++++++++++-------------
>  1 file changed, 12 insertions(+), 13 deletions(-)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index
> e335330..c843652 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1408,29 +1408,27 @@ struct mem_info
> *sample__resolve_mem(struct perf_sample *sample,  static int
> add_callchain_ip(struct thread *thread,
>  			    struct symbol **parent,
>  			    struct addr_location *root_al,
> -			    bool branch_history,
> +			    u8 *cpumode,
>  			    u64 ip)
>  {
>  	struct addr_location al;
> 
>  	al.filtered = 0;
>  	al.sym = NULL;
> -	if (branch_history)
> +	if (!cpumode) {
>  		thread__find_cpumode_addr_location(thread,
> MAP__FUNCTION,
>  						   ip, &al);
> -	else {
> -		u8 cpumode = PERF_RECORD_MISC_USER;
> -
> +	} else {
>  		if (ip >= PERF_CONTEXT_MAX) {
>  			switch (ip) {
>  			case PERF_CONTEXT_HV:
> -				cpumode =
> PERF_RECORD_MISC_HYPERVISOR;
> +				*cpumode =
> PERF_RECORD_MISC_HYPERVISOR;
>  				break;
>  			case PERF_CONTEXT_KERNEL:
> -				cpumode = PERF_RECORD_MISC_KERNEL;
> +				*cpumode = PERF_RECORD_MISC_KERNEL;
>  				break;
>  			case PERF_CONTEXT_USER:
> -				cpumode = PERF_RECORD_MISC_USER;
> +				*cpumode = PERF_RECORD_MISC_USER;
>  				break;
>  			default:
>  				pr_debug("invalid callchain context: "
> @@ -1444,8 +1442,8 @@ static int add_callchain_ip(struct thread *thread,
>  			}
>  			return 0;
>  		}
> -		thread__find_addr_location(thread, cpumode,
> MAP__FUNCTION,
> -				   ip, &al);
> +		thread__find_addr_location(thread, *cpumode,
> MAP__FUNCTION,
> +					   ip, &al);
>  	}
> 
>  	if (al.sym != NULL) {
> @@ -1604,6 +1602,7 @@ static int
> thread__resolve_callchain_sample(struct thread *thread,
>  	struct branch_stack *branch = sample->branch_stack;
>  	struct ip_callchain *chain = sample->callchain;
>  	int chain_nr = min(max_stack, (int)chain->nr);
> +	u8 cpumode = PERF_RECORD_MISC_USER;
>  	int i, j, err;
>  	int skip_idx = -1;
>  	int first_call = 0;
> @@ -1669,10 +1668,10 @@ static int
> thread__resolve_callchain_sample(struct thread *thread,
> 
>  		for (i = 0; i < nr; i++) {
>  			err = add_callchain_ip(thread, parent, root_al,
> -					       true, be[i].to);
> +					       NULL, be[i].to);
>  			if (!err)
>  				err = add_callchain_ip(thread, parent,
> root_al,
> -						       true, be[i].from);
> +						       NULL, be[i].from);
>  			if (err == -EINVAL)
>  				break;
>  			if (err)
> @@ -1701,7 +1700,7 @@ check_calls:
>  #endif
>  		ip = chain->ips[j];
> 
> -		err = add_callchain_ip(thread, parent, root_al, false, ip);
> +		err = add_callchain_ip(thread, parent, root_al, &cpumode,
> ip);
> 
>  		if (err)
>  			return (err < 0) ? err : 0;
> --
> 2.1.4

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