2022-09-22 19:03:30

by kernel test robot

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Subject: [dvyukov:dvyukov-perf-debugging 1/1] arch/x86/kernel/hw_breakpoint.c:101:29: warning: variable 'copy' set but not used

tree: https://github.com/dvyukov/linux dvyukov-perf-debugging
head: 62267cd404c44bbb18a96c108839c99e7ba6f9bd
commit: 62267cd404c44bbb18a96c108839c99e7ba6f9bd [1/1] perf: debugging of missed breakpoints
config: i386-tinyconfig (https://download.01.org/0day-ci/archive/20220923/[email protected]/config)
compiler: gcc-11 (Debian 11.3.0-5) 11.3.0
reproduce (this is a W=1 build):
# https://github.com/dvyukov/linux/commit/62267cd404c44bbb18a96c108839c99e7ba6f9bd
git remote add dvyukov https://github.com/dvyukov/linux
git fetch --no-tags dvyukov dvyukov-perf-debugging
git checkout 62267cd404c44bbb18a96c108839c99e7ba6f9bd
# save the config file
mkdir build_dir && cp config build_dir/.config
make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kernel/ kernel/events/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <[email protected]>

All warnings (new ones prefixed by >>):

arch/x86/kernel/hw_breakpoint.c: In function 'arch_install_hw_breakpoint':
>> arch/x86/kernel/hw_breakpoint.c:101:29: warning: variable 'copy' set but not used [-Wunused-but-set-variable]
101 | unsigned long *dr7, copy;
| ^~~~
arch/x86/kernel/hw_breakpoint.c: In function 'arch_uninstall_hw_breakpoint':
arch/x86/kernel/hw_breakpoint.c:151:28: warning: variable 'copy' set but not used [-Wunused-but-set-variable]
151 | unsigned long dr7, copy;
| ^~~~
arch/x86/kernel/hw_breakpoint.c: In function 'hw_breakpoint_handler':
>> arch/x86/kernel/hw_breakpoint.c:578:37: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]
578 | LOG("HIT not found");
| ^
--
kernel/events/core.c: In function 'perf_event_disable_inatomic':
>> kernel/events/core.c:2474:74: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]
2474 | LOG("perf_event_disable_inatomic: irq_work_queue FAILED");
| ^
kernel/events/core.c: In function 'merge_sched_in':
>> kernel/events/core.c:3739:53: warning: suggest braces around empty body in an 'else' statement [-Wempty-body]
3739 | LOG("group_sched_in failed");
| ^
kernel/events/core.c: In function 'perf_bp_event':
kernel/events/core.c:10191:45: warning: suggest braces around empty body in an 'else' statement [-Wempty-body]
10191 | LOG("perf_bp_event: ignore");
| ^


vim +/copy +101 arch/x86/kernel/hw_breakpoint.c

88
89 /*
90 * Install a perf counter breakpoint.
91 *
92 * We seek a free debug address register and use it for this
93 * breakpoint. Eventually we enable it in the debug control register.
94 *
95 * Atomic: we hold the counter->ctx->lock and we only handle variables
96 * and registers local to this cpu.
97 */
98 int arch_install_hw_breakpoint(struct perf_event *bp)
99 {
100 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
> 101 unsigned long *dr7, copy;
102 int i;
103
104 lockdep_assert_irqs_disabled();
105
106 for (i = 0; i < HBP_NUM; i++) {
107 struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
108
109 if (!*slot) {
110 *slot = bp;
111 break;
112 }
113 }
114
115 if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
116 return -EBUSY;
117
118 set_debugreg(info->address, i);
119 __this_cpu_write(cpu_debugreg[i], info->address);
120
121 dr7 = this_cpu_ptr(&cpu_dr7);
122 copy = *dr7;
123 *dr7 |= encode_dr7(i, info->len, info->type);
124 //LOG("INSTALL slot=%d event=%p", i, bp);
125
126 /*
127 * Ensure we first write cpu_dr7 before we set the DR7 register.
128 * This ensures an NMI never see cpu_dr7 0 when DR7 is not.
129 */
130 barrier();
131
132 set_debugreg(*dr7, 7);
133 if (info->mask)
134 set_dr_addr_mask(info->mask, i);
135
136 return 0;
137 }
138

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