| Message ID | 1448622572-16900-2-git-send-email-pmladek@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Petr,
[auto build test WARNING on powerpc/next]
[also build test WARNING on v4.4-rc2 next-20151127]
[cannot apply to tip/x86/core]
url: https://github.com/0day-ci/linux/commits/Petr-Mladek/Cleaning-printk-stuff-in-NMI-context/20151127-191620
base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: mn10300-asb2364_defconfig (attached as .config)
reproduce:
wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=mn10300
All warnings (new ones prefixed by >>):
warning: (MN10300) selects HAVE_NMI_WATCHDOG which has unmet direct dependencies (HAVE_NMI)
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
Hi Petr,
[auto build test ERROR on: powerpc/next]
[also build test ERROR on: v4.4-rc2 next-20151127]
[cannot apply to: tip/x86/core]
url: https://github.com/0day-ci/linux/commits/Petr-Mladek/Cleaning-printk-stuff-in-NMI-context/20151127-191620
base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: i386-randconfig-s1-201547 (attached as .config)
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
All error/warnings (new ones prefixed by >>):
In file included from arch/x86/include/asm/percpu.h:551:0,
from arch/x86/include/asm/current.h:5,
from arch/x86/include/asm/processor.h:15,
from arch/x86/include/asm/atomic.h:6,
from include/linux/atomic.h:4,
from include/linux/llist.h:58,
from include/linux/smp.h:14,
from kernel/printk/nmi.c:18:
kernel/printk/printk.h: In function 'vprintk_func':
>> include/asm-generic/percpu.h:111:2: error: implicit declaration of function 'preempt_disable' [-Werror=implicit-function-declaration]
preempt_disable(); \
^
>> include/asm-generic/percpu.h:305:31: note: in expansion of macro 'this_cpu_generic_read'
#define this_cpu_read_8(pcp) this_cpu_generic_read(pcp)
^
>> include/linux/percpu-defs.h:311:23: note: in expansion of macro 'this_cpu_read_8'
case 8: pscr_ret__ = stem##8(variable); break; \
^
>> include/linux/percpu-defs.h:494:29: note: in expansion of macro '__pcpu_size_call_return'
#define this_cpu_read(pcp) __pcpu_size_call_return(this_cpu_read_, pcp)
^
>> kernel/printk/printk.h:34:9: note: in expansion of macro 'this_cpu_read'
return this_cpu_read(printk_func)(fmt, args);
^
>> include/asm-generic/percpu.h:113:2: error: implicit declaration of function 'preempt_enable' [-Werror=implicit-function-declaration]
preempt_enable(); \
^
>> include/asm-generic/percpu.h:305:31: note: in expansion of macro 'this_cpu_generic_read'
#define this_cpu_read_8(pcp) this_cpu_generic_read(pcp)
^
>> include/linux/percpu-defs.h:311:23: note: in expansion of macro 'this_cpu_read_8'
case 8: pscr_ret__ = stem##8(variable); break; \
^
>> include/linux/percpu-defs.h:494:29: note: in expansion of macro '__pcpu_size_call_return'
#define this_cpu_read(pcp) __pcpu_size_call_return(this_cpu_read_, pcp)
^
>> kernel/printk/printk.h:34:9: note: in expansion of macro 'this_cpu_read'
return this_cpu_read(printk_func)(fmt, args);
^
kernel/printk/nmi.c: In function '__printk_nmi_flush':
>> kernel/printk/nmi.c:106:9: error: unknown type name 'raw_spinlock_t'
static raw_spinlock_t read_lock =
^
>> kernel/printk/nmi.c:107:3: error: implicit declaration of function '__RAW_SPIN_LOCK_INITIALIZER' [-Werror=implicit-function-declaration]
__RAW_SPIN_LOCK_INITIALIZER(read_lock);
^
>> kernel/printk/nmi.c:107:3: error: initializer element is not constant
>> kernel/printk/nmi.c:118:2: error: implicit declaration of function 'raw_spin_lock' [-Werror=implicit-function-declaration]
raw_spin_lock(&read_lock);
^
>> kernel/printk/nmi.c:163:2: error: implicit declaration of function 'raw_spin_unlock' [-Werror=implicit-function-declaration]
raw_spin_unlock(&read_lock);
^
cc1: some warnings being treated as errors
vim +/preempt_disable +111 include/asm-generic/percpu.h
9c28278a24 Tejun Heo 2014-06-17 105 (__ret); \
9c28278a24 Tejun Heo 2014-06-17 106 })
9c28278a24 Tejun Heo 2014-06-17 107
eba117889a Tejun Heo 2014-06-17 108 #define this_cpu_generic_read(pcp) \
eba117889a Tejun Heo 2014-06-17 109 ({ \
eba117889a Tejun Heo 2014-06-17 110 typeof(pcp) __ret; \
9c28278a24 Tejun Heo 2014-06-17 @111 preempt_disable(); \
eba117889a Tejun Heo 2014-06-17 112 __ret = *this_cpu_ptr(&(pcp)); \
9c28278a24 Tejun Heo 2014-06-17 @113 preempt_enable(); \
eba117889a Tejun Heo 2014-06-17 114 __ret; \
9c28278a24 Tejun Heo 2014-06-17 115 })
9c28278a24 Tejun Heo 2014-06-17 116
eba117889a Tejun Heo 2014-06-17 117 #define this_cpu_generic_to_op(pcp, val, op) \
9c28278a24 Tejun Heo 2014-06-17 118 do { \
eba117889a Tejun Heo 2014-06-17 119 unsigned long __flags; \
eba117889a Tejun Heo 2014-06-17 120 raw_local_irq_save(__flags); \
9c28278a24 Tejun Heo 2014-06-17 121 *raw_cpu_ptr(&(pcp)) op val; \
eba117889a Tejun Heo 2014-06-17 122 raw_local_irq_restore(__flags); \
9c28278a24 Tejun Heo 2014-06-17 123 } while (0)
9c28278a24 Tejun Heo 2014-06-17 124
eba117889a Tejun Heo 2014-06-17 125 #define this_cpu_generic_add_return(pcp, val) \
9c28278a24 Tejun Heo 2014-06-17 126 ({ \
eba117889a Tejun Heo 2014-06-17 127 typeof(pcp) __ret; \
eba117889a Tejun Heo 2014-06-17 128 unsigned long __flags; \
eba117889a Tejun Heo 2014-06-17 129 raw_local_irq_save(__flags); \
9c28278a24 Tejun Heo 2014-06-17 130 raw_cpu_add(pcp, val); \
eba117889a Tejun Heo 2014-06-17 131 __ret = raw_cpu_read(pcp); \
eba117889a Tejun Heo 2014-06-17 132 raw_local_irq_restore(__flags); \
eba117889a Tejun Heo 2014-06-17 133 __ret; \
9c28278a24 Tejun Heo 2014-06-17 134 })
9c28278a24 Tejun Heo 2014-06-17 135
eba117889a Tejun Heo 2014-06-17 136 #define this_cpu_generic_xchg(pcp, nval) \
eba117889a Tejun Heo 2014-06-17 137 ({ \
eba117889a Tejun Heo 2014-06-17 138 typeof(pcp) __ret; \
eba117889a Tejun Heo 2014-06-17 139 unsigned long __flags; \
eba117889a Tejun Heo 2014-06-17 140 raw_local_irq_save(__flags); \
eba117889a Tejun Heo 2014-06-17 141 __ret = raw_cpu_read(pcp); \
9c28278a24 Tejun Heo 2014-06-17 142 raw_cpu_write(pcp, nval); \
eba117889a Tejun Heo 2014-06-17 143 raw_local_irq_restore(__flags); \
eba117889a Tejun Heo 2014-06-17 144 __ret; \
9c28278a24 Tejun Heo 2014-06-17 145 })
9c28278a24 Tejun Heo 2014-06-17 146
eba117889a Tejun Heo 2014-06-17 147 #define this_cpu_generic_cmpxchg(pcp, oval, nval) \
9c28278a24 Tejun Heo 2014-06-17 148 ({ \
eba117889a Tejun Heo 2014-06-17 149 typeof(pcp) __ret; \
eba117889a Tejun Heo 2014-06-17 150 unsigned long __flags; \
eba117889a Tejun Heo 2014-06-17 151 raw_local_irq_save(__flags); \
eba117889a Tejun Heo 2014-06-17 152 __ret = raw_cpu_read(pcp); \
eba117889a Tejun Heo 2014-06-17 153 if (__ret == (oval)) \
9c28278a24 Tejun Heo 2014-06-17 154 raw_cpu_write(pcp, nval); \
eba117889a Tejun Heo 2014-06-17 155 raw_local_irq_restore(__flags); \
eba117889a Tejun Heo 2014-06-17 156 __ret; \
9c28278a24 Tejun Heo 2014-06-17 157 })
9c28278a24 Tejun Heo 2014-06-17 158
eba117889a Tejun Heo 2014-06-17 159 #define this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
9c28278a24 Tejun Heo 2014-06-17 160 ({ \
eba117889a Tejun Heo 2014-06-17 161 int __ret; \
eba117889a Tejun Heo 2014-06-17 162 unsigned long __flags; \
eba117889a Tejun Heo 2014-06-17 163 raw_local_irq_save(__flags); \
eba117889a Tejun Heo 2014-06-17 164 __ret = raw_cpu_generic_cmpxchg_double(pcp1, pcp2, \
9c28278a24 Tejun Heo 2014-06-17 165 oval1, oval2, nval1, nval2); \
eba117889a Tejun Heo 2014-06-17 166 raw_local_irq_restore(__flags); \
eba117889a Tejun Heo 2014-06-17 167 __ret; \
9c28278a24 Tejun Heo 2014-06-17 168 })
9c28278a24 Tejun Heo 2014-06-17 169
47b69ad673 Tejun Heo 2014-06-17 170 #ifndef raw_cpu_read_1
47b69ad673 Tejun Heo 2014-06-17 171 #define raw_cpu_read_1(pcp) (*raw_cpu_ptr(&(pcp)))
47b69ad673 Tejun Heo 2014-06-17 172 #endif
47b69ad673 Tejun Heo 2014-06-17 173 #ifndef raw_cpu_read_2
47b69ad673 Tejun Heo 2014-06-17 174 #define raw_cpu_read_2(pcp) (*raw_cpu_ptr(&(pcp)))
47b69ad673 Tejun Heo 2014-06-17 175 #endif
47b69ad673 Tejun Heo 2014-06-17 176 #ifndef raw_cpu_read_4
47b69ad673 Tejun Heo 2014-06-17 177 #define raw_cpu_read_4(pcp) (*raw_cpu_ptr(&(pcp)))
47b69ad673 Tejun Heo 2014-06-17 178 #endif
47b69ad673 Tejun Heo 2014-06-17 179 #ifndef raw_cpu_read_8
47b69ad673 Tejun Heo 2014-06-17 180 #define raw_cpu_read_8(pcp) (*raw_cpu_ptr(&(pcp)))
47b69ad673 Tejun Heo 2014-06-17 181 #endif
47b69ad673 Tejun Heo 2014-06-17 182
47b69ad673 Tejun Heo 2014-06-17 183 #ifndef raw_cpu_write_1
eba117889a Tejun Heo 2014-06-17 184 #define raw_cpu_write_1(pcp, val) raw_cpu_generic_to_op(pcp, val, =)
47b69ad673 Tejun Heo 2014-06-17 185 #endif
47b69ad673 Tejun Heo 2014-06-17 186 #ifndef raw_cpu_write_2
eba117889a Tejun Heo 2014-06-17 187 #define raw_cpu_write_2(pcp, val) raw_cpu_generic_to_op(pcp, val, =)
47b69ad673 Tejun Heo 2014-06-17 188 #endif
47b69ad673 Tejun Heo 2014-06-17 189 #ifndef raw_cpu_write_4
eba117889a Tejun Heo 2014-06-17 190 #define raw_cpu_write_4(pcp, val) raw_cpu_generic_to_op(pcp, val, =)
47b69ad673 Tejun Heo 2014-06-17 191 #endif
47b69ad673 Tejun Heo 2014-06-17 192 #ifndef raw_cpu_write_8
eba117889a Tejun Heo 2014-06-17 193 #define raw_cpu_write_8(pcp, val) raw_cpu_generic_to_op(pcp, val, =)
47b69ad673 Tejun Heo 2014-06-17 194 #endif
47b69ad673 Tejun Heo 2014-06-17 195
47b69ad673 Tejun Heo 2014-06-17 196 #ifndef raw_cpu_add_1
eba117889a Tejun Heo 2014-06-17 197 #define raw_cpu_add_1(pcp, val) raw_cpu_generic_to_op(pcp, val, +=)
47b69ad673 Tejun Heo 2014-06-17 198 #endif
47b69ad673 Tejun Heo 2014-06-17 199 #ifndef raw_cpu_add_2
eba117889a Tejun Heo 2014-06-17 200 #define raw_cpu_add_2(pcp, val) raw_cpu_generic_to_op(pcp, val, +=)
47b69ad673 Tejun Heo 2014-06-17 201 #endif
47b69ad673 Tejun Heo 2014-06-17 202 #ifndef raw_cpu_add_4
eba117889a Tejun Heo 2014-06-17 203 #define raw_cpu_add_4(pcp, val) raw_cpu_generic_to_op(pcp, val, +=)
47b69ad673 Tejun Heo 2014-06-17 204 #endif
47b69ad673 Tejun Heo 2014-06-17 205 #ifndef raw_cpu_add_8
eba117889a Tejun Heo 2014-06-17 206 #define raw_cpu_add_8(pcp, val) raw_cpu_generic_to_op(pcp, val, +=)
47b69ad673 Tejun Heo 2014-06-17 207 #endif
47b69ad673 Tejun Heo 2014-06-17 208
47b69ad673 Tejun Heo 2014-06-17 209 #ifndef raw_cpu_and_1
eba117889a Tejun Heo 2014-06-17 210 #define raw_cpu_and_1(pcp, val) raw_cpu_generic_to_op(pcp, val, &=)
47b69ad673 Tejun Heo 2014-06-17 211 #endif
47b69ad673 Tejun Heo 2014-06-17 212 #ifndef raw_cpu_and_2
eba117889a Tejun Heo 2014-06-17 213 #define raw_cpu_and_2(pcp, val) raw_cpu_generic_to_op(pcp, val, &=)
47b69ad673 Tejun Heo 2014-06-17 214 #endif
47b69ad673 Tejun Heo 2014-06-17 215 #ifndef raw_cpu_and_4
eba117889a Tejun Heo 2014-06-17 216 #define raw_cpu_and_4(pcp, val) raw_cpu_generic_to_op(pcp, val, &=)
47b69ad673 Tejun Heo 2014-06-17 217 #endif
47b69ad673 Tejun Heo 2014-06-17 218 #ifndef raw_cpu_and_8
eba117889a Tejun Heo 2014-06-17 219 #define raw_cpu_and_8(pcp, val) raw_cpu_generic_to_op(pcp, val, &=)
47b69ad673 Tejun Heo 2014-06-17 220 #endif
47b69ad673 Tejun Heo 2014-06-17 221
47b69ad673 Tejun Heo 2014-06-17 222 #ifndef raw_cpu_or_1
eba117889a Tejun Heo 2014-06-17 223 #define raw_cpu_or_1(pcp, val) raw_cpu_generic_to_op(pcp, val, |=)
47b69ad673 Tejun Heo 2014-06-17 224 #endif
47b69ad673 Tejun Heo 2014-06-17 225 #ifndef raw_cpu_or_2
eba117889a Tejun Heo 2014-06-17 226 #define raw_cpu_or_2(pcp, val) raw_cpu_generic_to_op(pcp, val, |=)
47b69ad673 Tejun Heo 2014-06-17 227 #endif
47b69ad673 Tejun Heo 2014-06-17 228 #ifndef raw_cpu_or_4
eba117889a Tejun Heo 2014-06-17 229 #define raw_cpu_or_4(pcp, val) raw_cpu_generic_to_op(pcp, val, |=)
47b69ad673 Tejun Heo 2014-06-17 230 #endif
47b69ad673 Tejun Heo 2014-06-17 231 #ifndef raw_cpu_or_8
eba117889a Tejun Heo 2014-06-17 232 #define raw_cpu_or_8(pcp, val) raw_cpu_generic_to_op(pcp, val, |=)
47b69ad673 Tejun Heo 2014-06-17 233 #endif
47b69ad673 Tejun Heo 2014-06-17 234
47b69ad673 Tejun Heo 2014-06-17 235 #ifndef raw_cpu_add_return_1
47b69ad673 Tejun Heo 2014-06-17 236 #define raw_cpu_add_return_1(pcp, val) raw_cpu_generic_add_return(pcp, val)
47b69ad673 Tejun Heo 2014-06-17 237 #endif
47b69ad673 Tejun Heo 2014-06-17 238 #ifndef raw_cpu_add_return_2
47b69ad673 Tejun Heo 2014-06-17 239 #define raw_cpu_add_return_2(pcp, val) raw_cpu_generic_add_return(pcp, val)
47b69ad673 Tejun Heo 2014-06-17 240 #endif
47b69ad673 Tejun Heo 2014-06-17 241 #ifndef raw_cpu_add_return_4
47b69ad673 Tejun Heo 2014-06-17 242 #define raw_cpu_add_return_4(pcp, val) raw_cpu_generic_add_return(pcp, val)
47b69ad673 Tejun Heo 2014-06-17 243 #endif
47b69ad673 Tejun Heo 2014-06-17 244 #ifndef raw_cpu_add_return_8
47b69ad673 Tejun Heo 2014-06-17 245 #define raw_cpu_add_return_8(pcp, val) raw_cpu_generic_add_return(pcp, val)
47b69ad673 Tejun Heo 2014-06-17 246 #endif
47b69ad673 Tejun Heo 2014-06-17 247
47b69ad673 Tejun Heo 2014-06-17 248 #ifndef raw_cpu_xchg_1
47b69ad673 Tejun Heo 2014-06-17 249 #define raw_cpu_xchg_1(pcp, nval) raw_cpu_generic_xchg(pcp, nval)
47b69ad673 Tejun Heo 2014-06-17 250 #endif
47b69ad673 Tejun Heo 2014-06-17 251 #ifndef raw_cpu_xchg_2
47b69ad673 Tejun Heo 2014-06-17 252 #define raw_cpu_xchg_2(pcp, nval) raw_cpu_generic_xchg(pcp, nval)
47b69ad673 Tejun Heo 2014-06-17 253 #endif
47b69ad673 Tejun Heo 2014-06-17 254 #ifndef raw_cpu_xchg_4
47b69ad673 Tejun Heo 2014-06-17 255 #define raw_cpu_xchg_4(pcp, nval) raw_cpu_generic_xchg(pcp, nval)
47b69ad673 Tejun Heo 2014-06-17 256 #endif
47b69ad673 Tejun Heo 2014-06-17 257 #ifndef raw_cpu_xchg_8
47b69ad673 Tejun Heo 2014-06-17 258 #define raw_cpu_xchg_8(pcp, nval) raw_cpu_generic_xchg(pcp, nval)
47b69ad673 Tejun Heo 2014-06-17 259 #endif
47b69ad673 Tejun Heo 2014-06-17 260
47b69ad673 Tejun Heo 2014-06-17 261 #ifndef raw_cpu_cmpxchg_1
eba117889a Tejun Heo 2014-06-17 262 #define raw_cpu_cmpxchg_1(pcp, oval, nval) \
eba117889a Tejun Heo 2014-06-17 263 raw_cpu_generic_cmpxchg(pcp, oval, nval)
47b69ad673 Tejun Heo 2014-06-17 264 #endif
47b69ad673 Tejun Heo 2014-06-17 265 #ifndef raw_cpu_cmpxchg_2
eba117889a Tejun Heo 2014-06-17 266 #define raw_cpu_cmpxchg_2(pcp, oval, nval) \
eba117889a Tejun Heo 2014-06-17 267 raw_cpu_generic_cmpxchg(pcp, oval, nval)
47b69ad673 Tejun Heo 2014-06-17 268 #endif
47b69ad673 Tejun Heo 2014-06-17 269 #ifndef raw_cpu_cmpxchg_4
eba117889a Tejun Heo 2014-06-17 270 #define raw_cpu_cmpxchg_4(pcp, oval, nval) \
eba117889a Tejun Heo 2014-06-17 271 raw_cpu_generic_cmpxchg(pcp, oval, nval)
47b69ad673 Tejun Heo 2014-06-17 272 #endif
47b69ad673 Tejun Heo 2014-06-17 273 #ifndef raw_cpu_cmpxchg_8
eba117889a Tejun Heo 2014-06-17 274 #define raw_cpu_cmpxchg_8(pcp, oval, nval) \
eba117889a Tejun Heo 2014-06-17 275 raw_cpu_generic_cmpxchg(pcp, oval, nval)
47b69ad673 Tejun Heo 2014-06-17 276 #endif
47b69ad673 Tejun Heo 2014-06-17 277
47b69ad673 Tejun Heo 2014-06-17 278 #ifndef raw_cpu_cmpxchg_double_1
47b69ad673 Tejun Heo 2014-06-17 279 #define raw_cpu_cmpxchg_double_1(pcp1, pcp2, oval1, oval2, nval1, nval2) \
47b69ad673 Tejun Heo 2014-06-17 280 raw_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
47b69ad673 Tejun Heo 2014-06-17 281 #endif
47b69ad673 Tejun Heo 2014-06-17 282 #ifndef raw_cpu_cmpxchg_double_2
47b69ad673 Tejun Heo 2014-06-17 283 #define raw_cpu_cmpxchg_double_2(pcp1, pcp2, oval1, oval2, nval1, nval2) \
47b69ad673 Tejun Heo 2014-06-17 284 raw_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
47b69ad673 Tejun Heo 2014-06-17 285 #endif
47b69ad673 Tejun Heo 2014-06-17 286 #ifndef raw_cpu_cmpxchg_double_4
47b69ad673 Tejun Heo 2014-06-17 287 #define raw_cpu_cmpxchg_double_4(pcp1, pcp2, oval1, oval2, nval1, nval2) \
47b69ad673 Tejun Heo 2014-06-17 288 raw_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
47b69ad673 Tejun Heo 2014-06-17 289 #endif
47b69ad673 Tejun Heo 2014-06-17 290 #ifndef raw_cpu_cmpxchg_double_8
47b69ad673 Tejun Heo 2014-06-17 291 #define raw_cpu_cmpxchg_double_8(pcp1, pcp2, oval1, oval2, nval1, nval2) \
47b69ad673 Tejun Heo 2014-06-17 292 raw_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
47b69ad673 Tejun Heo 2014-06-17 293 #endif
47b69ad673 Tejun Heo 2014-06-17 294
47b69ad673 Tejun Heo 2014-06-17 295 #ifndef this_cpu_read_1
eba117889a Tejun Heo 2014-06-17 296 #define this_cpu_read_1(pcp) this_cpu_generic_read(pcp)
47b69ad673 Tejun Heo 2014-06-17 297 #endif
47b69ad673 Tejun Heo 2014-06-17 298 #ifndef this_cpu_read_2
eba117889a Tejun Heo 2014-06-17 299 #define this_cpu_read_2(pcp) this_cpu_generic_read(pcp)
47b69ad673 Tejun Heo 2014-06-17 300 #endif
47b69ad673 Tejun Heo 2014-06-17 301 #ifndef this_cpu_read_4
eba117889a Tejun Heo 2014-06-17 302 #define this_cpu_read_4(pcp) this_cpu_generic_read(pcp)
47b69ad673 Tejun Heo 2014-06-17 303 #endif
47b69ad673 Tejun Heo 2014-06-17 304 #ifndef this_cpu_read_8
eba117889a Tejun Heo 2014-06-17 @305 #define this_cpu_read_8(pcp) this_cpu_generic_read(pcp)
47b69ad673 Tejun Heo 2014-06-17 306 #endif
47b69ad673 Tejun Heo 2014-06-17 307
47b69ad673 Tejun Heo 2014-06-17 308 #ifndef this_cpu_write_1
:::::: The code at line 111 was first introduced by commit
:::::: 9c28278a24c01c0073fb89e53c1d2a605ab9587d percpu: reorder macros in percpu header files
:::::: TO: Tejun Heo <tj@kernel.org>
:::::: CC: Tejun Heo <tj@kernel.org>
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
Hi Peter, On Fri, Nov 27, 2015 at 2:09 PM, Petr Mladek <pmladek@suse.com> wrote: > printk() takes some locks and could not be used a safe way in NMI > context. > > The chance of a deadlock is real especially when printing > stacks from all CPUs. This particular problem has been addressed > on x86 by the commit a9edc8809328 ("x86/nmi: Perform a safe NMI stack > trace on all CPUs"). > > This patch reuses most of the code and makes it generic. It is > useful for all messages and architectures that support NMI. > > The alternative printk_func is set when entering and is reseted when > leaving NMI context. It queues IRQ work to copy the messages into > the main ring buffer in a safe context. > > __printk_nmi_flush() copies all available messages and reset > the buffer. Then we could use a simple cmpxchg operations to > get synchronized with writers. There is also used a spinlock > to get synchronized with other flushers. > > We do not longer use seq_buf because it depends on external lock. > It would be hard to make all supported operations safe for > a lockless use. It would be confusing and error prone to > make only some operations safe. > > The code is put into separate printk/nmi.c as suggested by > Steven Rostedt. It needs a per-CPU buffer and is compiled only > on architectures that call nmi_enter(). This is achieved by > the new HAVE_NMI Kconfig flag. > > One exception is arm where the deferred printing is used for > printing backtraces even without NMI. For this purpose, > we define NEED_PRINTK_NMI Kconfig flag. The alternative > printk_func is explicitly set when IPI_CPU_BACKTRACE is > handled. > > Another exception is Xtensa architecture that uses just a > fake NMI. It's called fake because it's actually maskable, but sometimes it is safe to use it as NMI (when there are no other IRQs at the same priority level and that level equals EXCM level). That condition is checked in arch/xtensa/include/asm/processor.h So 'fake' here is to avoid confusion with real NMI that exists on xtensa (and is not currently used in linux), otherwise code that runs in fake NMI must follow the NMI rules. To make xtensa compatible with your change we can add a choice whether fake NMI should be used to kconfig. It can then set HAVE_NMI accordingly. I'll post a patch for xtensa.
On Fri 2015-11-27 17:26:16, Max Filippov wrote: Hi Max, > > Another exception is Xtensa architecture that uses just a > > fake NMI. > > It's called fake because it's actually maskable, but sometimes > it is safe to use it as NMI (when there are no other IRQs at the > same priority level and that level equals EXCM level). That > condition is checked in arch/xtensa/include/asm/processor.h > So 'fake' here is to avoid confusion with real NMI that exists > on xtensa (and is not currently used in linux), otherwise code > that runs in fake NMI must follow the NMI rules. > > To make xtensa compatible with your change we can add a > choice whether fake NMI should be used to kconfig. It can > then set HAVE_NMI accordingly. I'll post a patch for xtensa. Thanks a lot for explanation. I'll wait for the destiny of the patch adding CONFIG_XTENSA_FAKE_NMI. It is not easy for me to review. Anyway, we could select HAVE_NMI for Xtensa anytime later if this patchset goes in earlier. Best Regards, Petr
On Fri, 2015-11-27 at 12:09 +0100, Petr Mladek wrote: > printk() takes some locks and could not be used a safe way in NMI > context. > > The chance of a deadlock is real especially when printing > stacks from all CPUs. This particular problem has been addressed > on x86 by the commit a9edc8809328 ("x86/nmi: Perform a safe NMI stack > trace on all CPUs"). ... > diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c > new file mode 100644 > index 000000000000..3989e13a0021 > --- /dev/null > +++ b/kernel/printk/nmi.c > @@ -0,0 +1,200 @@ ... > + > +struct nmi_seq_buf { > + atomic_t len; /* length of written data */ > + struct irq_work work; /* IRQ work that flushes the buffer */ > + unsigned char buffer[PAGE_SIZE - sizeof(atomic_t) - > + sizeof(struct irq_work)]; > +}; > +static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq); PAGE_SIZE isn't always 4K. On typical powerpc systems this will give you 128K, and on some 512K, which is probably not what we wanted. The existing code just did: #define NMI_BUF_SIZE 4096 So I think you should just go back to doing that. cheers
On Wed 2015-12-02 13:45:16, Michael Ellerman wrote: > On Fri, 2015-11-27 at 12:09 +0100, Petr Mladek wrote: > > > printk() takes some locks and could not be used a safe way in NMI > > context. > > > > The chance of a deadlock is real especially when printing > > stacks from all CPUs. This particular problem has been addressed > > on x86 by the commit a9edc8809328 ("x86/nmi: Perform a safe NMI stack > > trace on all CPUs"). > > ... > > > diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c > > new file mode 100644 > > index 000000000000..3989e13a0021 > > --- /dev/null > > +++ b/kernel/printk/nmi.c > > @@ -0,0 +1,200 @@ > > ... > > > + > > +struct nmi_seq_buf { > > + atomic_t len; /* length of written data */ > > + struct irq_work work; /* IRQ work that flushes the buffer */ > > + unsigned char buffer[PAGE_SIZE - sizeof(atomic_t) - > > + sizeof(struct irq_work)]; > > +}; > > +static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq); > > > PAGE_SIZE isn't always 4K. > > On typical powerpc systems this will give you 128K, and on some 512K, which is > probably not what we wanted. Good point! > The existing code just did: > > #define NMI_BUF_SIZE 4096 I will change this to 8192. The 4kB were not enough in some cases. Best Regards, Petr
diff --git a/arch/Kconfig b/arch/Kconfig index 4e949e58b192..7ce5101c2472 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -187,7 +187,14 @@ config HAVE_OPTPROBES config HAVE_KPROBES_ON_FTRACE bool +config HAVE_NMI + bool + +config NEED_PRINTK_NMI + bool + config HAVE_NMI_WATCHDOG + depends on HAVE_NMI bool # # An arch should select this if it provides all these things: diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 0365cbbc9179..f0465e420762 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -63,6 +63,8 @@ config ARM select HAVE_KRETPROBES if (HAVE_KPROBES) select HAVE_MEMBLOCK select HAVE_MOD_ARCH_SPECIFIC + select HAVE_NMI if (!CPU_V7M) + select NEED_PRINTK_NMI if (CPU_V7M) select HAVE_OPROFILE if (HAVE_PERF_EVENTS) select HAVE_OPTPROBES if !THUMB2_KERNEL select HAVE_PERF_EVENTS diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index b26361355dae..a960adb9bd7d 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -648,7 +648,9 @@ void handle_IPI(int ipinr, struct pt_regs *regs) case IPI_CPU_BACKTRACE: irq_enter(); + printk_nmi_enter(); nmi_cpu_backtrace(regs); + printk_nmi_exit(); irq_exit(); break; diff --git a/arch/avr32/Kconfig b/arch/avr32/Kconfig index b6878eb64884..9dc3e2b1180b 100644 --- a/arch/avr32/Kconfig +++ b/arch/avr32/Kconfig @@ -17,6 +17,7 @@ config AVR32 select GENERIC_CLOCKEVENTS select HAVE_MOD_ARCH_SPECIFIC select MODULES_USE_ELF_RELA + select HAVE_NMI help AVR32 is a high-performance 32-bit RISC microprocessor core, designed for cost-sensitive embedded applications, with particular diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig index af76634f8d98..47c0a55acafd 100644 --- a/arch/blackfin/Kconfig +++ b/arch/blackfin/Kconfig @@ -40,6 +40,7 @@ config BLACKFIN select HAVE_MOD_ARCH_SPECIFIC select MODULES_USE_ELF_RELA select HAVE_DEBUG_STACKOVERFLOW + select HAVE_NMI config GENERIC_CSUM def_bool y diff --git a/arch/cris/Kconfig b/arch/cris/Kconfig index e086f9e93728..62148eaf0189 100644 --- a/arch/cris/Kconfig +++ b/arch/cris/Kconfig @@ -69,6 +69,7 @@ config CRIS select GENERIC_CLOCKEVENTS if ETRAX_ARCH_V32 select GENERIC_SCHED_CLOCK if ETRAX_ARCH_V32 select HAVE_DEBUG_BUGVERBOSE if ETRAX_ARCH_V32 + select HAVE_NMI config HZ int diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 71683a853372..35ae01fe980a 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -63,6 +63,7 @@ config MIPS select HAVE_IRQ_TIME_ACCOUNTING select GENERIC_TIME_VSYSCALL select ARCH_CLOCKSOURCE_DATA + select HAVE_NMI menu "Machine selection" diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index db49e0d796b1..1bd8a7503a48 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -156,6 +156,7 @@ config PPC select NO_BOOTMEM select HAVE_GENERIC_RCU_GUP select HAVE_PERF_EVENTS_NMI if PPC64 + select HAVE_NMI if PERF_EVENTS select EDAC_SUPPORT select EDAC_ATOMIC_SCRUB select ARCH_HAS_DMA_SET_COHERENT_MASK diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 3a55f493c7da..9a8a76829508 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -159,6 +159,7 @@ config S390 select TTY select VIRT_CPU_ACCOUNTING select VIRT_TO_BUS + select HAVE_NMI config SCHED_OMIT_FRAME_POINTER diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index d514df7e04dd..ff8093b574f1 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -44,6 +44,7 @@ config SUPERH select OLD_SIGSUSPEND select OLD_SIGACTION select HAVE_ARCH_AUDITSYSCALL + select HAVE_NMI help The SuperH is a RISC processor targeted for use in embedded systems and consumer electronics; it was also used in the Sega Dreamcast diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index 56442d2d7bbc..e05ea973fd6a 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -80,6 +80,7 @@ config SPARC64 select NO_BOOTMEM select HAVE_ARCH_AUDITSYSCALL select ARCH_SUPPORTS_ATOMIC_RMW + select HAVE_NMI config ARCH_DEFCONFIG string diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig index 106c21bd7f44..050468c41dc6 100644 --- a/arch/tile/Kconfig +++ b/arch/tile/Kconfig @@ -29,6 +29,7 @@ config TILE select HAVE_DEBUG_STACKOVERFLOW select ARCH_WANT_FRAME_POINTERS select HAVE_CONTEXT_TRACKING + select HAVE_NMI if USE_PMC select EDAC_SUPPORT select GENERIC_STRNCPY_FROM_USER select GENERIC_STRNLEN_USER diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index db3622f22b61..e83f99194c4c 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -126,6 +126,7 @@ config X86 select HAVE_MEMBLOCK select HAVE_MEMBLOCK_NODE_MAP select HAVE_MIXED_BREAKPOINTS_REGS + select HAVE_NMI select HAVE_OPROFILE select HAVE_OPTPROBES select HAVE_PCSPKR_PLATFORM diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c index 045e424fb368..7788ce643bf4 100644 --- a/arch/x86/kernel/apic/hw_nmi.c +++ b/arch/x86/kernel/apic/hw_nmi.c @@ -18,7 +18,6 @@ #include <linux/nmi.h> #include <linux/module.h> #include <linux/delay.h> -#include <linux/seq_buf.h> #ifdef CONFIG_HARDLOCKUP_DETECTOR u64 hw_nmi_get_sample_period(int watchdog_thresh) diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index dfd59d6bc6f0..a477e0766d2e 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -67,10 +67,12 @@ extern void irq_exit(void); preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \ rcu_nmi_enter(); \ trace_hardirq_enter(); \ + printk_nmi_enter(); \ } while (0) #define nmi_exit() \ do { \ + printk_nmi_exit(); \ trace_hardirq_exit(); \ rcu_nmi_exit(); \ BUG_ON(!in_nmi()); \ diff --git a/include/linux/percpu.h b/include/linux/percpu.h index caebf2a758dc..04c68b9f56f8 100644 --- a/include/linux/percpu.h +++ b/include/linux/percpu.h @@ -135,7 +135,4 @@ extern phys_addr_t per_cpu_ptr_to_phys(void *addr); (typeof(type) __percpu *)__alloc_percpu(sizeof(type), \ __alignof__(type)) -/* To avoid include hell, as printk can not declare this, we declare it here */ -DECLARE_PER_CPU(printk_func_t, printk_func); - #endif /* __LINUX_PERCPU_H */ diff --git a/include/linux/printk.h b/include/linux/printk.h index 9729565c25ff..7aba6b92d020 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -122,7 +122,17 @@ static inline __printf(1, 2) __cold void early_printk(const char *s, ...) { } #endif -typedef __printf(1, 0) int (*printk_func_t)(const char *fmt, va_list args); +#ifdef CONFIG_PRINTK_NMI +extern void printk_nmi_init(void); +extern void printk_nmi_enter(void); +extern void printk_nmi_exit(void); +extern void printk_nmi_flush(void); +#else +static inline void printk_nmi_init(void) { } +static inline void printk_nmi_enter(void) { } +static inline void printk_nmi_exit(void) { } +static inline void printk_nmi_flush(void) { } +#endif /* PRINTK_NMI */ #ifdef CONFIG_PRINTK asmlinkage __printf(5, 0) diff --git a/init/Kconfig b/init/Kconfig index c24b6f767bf0..c1c0b6a2d712 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1456,6 +1456,11 @@ config PRINTK very difficult to diagnose system problems, saying N here is strongly discouraged. +config PRINTK_NMI + def_bool y + depends on PRINTK + depends on HAVE_NMI || NEED_PRINTK_NMI + config BUG bool "BUG() support" if EXPERT default y diff --git a/init/main.c b/init/main.c index 9e64d7097f1a..45c1e05125dc 100644 --- a/init/main.c +++ b/init/main.c @@ -591,6 +591,7 @@ asmlinkage __visible void __init start_kernel(void) timekeeping_init(); time_init(); sched_clock_postinit(); + printk_nmi_init(); perf_event_init(); profile_init(); call_function_init(); diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile index 85405bdcf2b3..abb0042a427b 100644 --- a/kernel/printk/Makefile +++ b/kernel/printk/Makefile @@ -1,2 +1,3 @@ obj-y = printk.o +obj-$(CONFIG_PRINTK_NMI) += nmi.o obj-$(CONFIG_A11Y_BRAILLE_CONSOLE) += braille.o diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c new file mode 100644 index 000000000000..3989e13a0021 --- /dev/null +++ b/kernel/printk/nmi.c @@ -0,0 +1,200 @@ +/* + * nmi.c - Safe printk in NMI context + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ + +#include <linux/smp.h> +#include <linux/cpumask.h> +#include <linux/irq_work.h> +#include <linux/printk.h> + +#include "printk.h" + +/* + * printk() could not take logbuf_lock in NMI context. Instead, + * it uses an alternative implementation that temporary stores + * the strings into a per-CPU buffer. The content of the buffer + * is later flushed into the main ring buffer via IRQ work. + * + * The alternative implementation is chosen transparently + * via @printk_func per-CPU variable. + * + * The implementation allows to flush the strings also from another CPU. + * There are situations when we want to make sure that all buffers + * were handled or when IRQs are blocked. + */ +DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default; + +struct nmi_seq_buf { + atomic_t len; /* length of written data */ + struct irq_work work; /* IRQ work that flushes the buffer */ + unsigned char buffer[PAGE_SIZE - sizeof(atomic_t) - + sizeof(struct irq_work)]; +}; +static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq); + +/* + * Safe printk() for NMI context. It uses a per-CPU buffer to + * store the message. NMIs are not nested, so there is always only + * one writer running. But the buffer might get flushed from another + * CPU, so we need to be careful. + */ +static int vprintk_nmi(const char *fmt, va_list args) +{ + struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq); + int add = 0, len; + +again: + len = atomic_read(&s->len); + + if (len >= sizeof(s->buffer)) + return 0; + + /* + * Make sure that all old data have been read before the buffer was + * reseted. This is not needed when we just append data. + */ + if (!len) + smp_rmb(); + + add = vsnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, args); + + /* + * Do it once again if the buffer has been flushed in the meantime. + * Note that atomic_cmpxchg() is an implicit memory barrier that + * makes sure that the data were written before updating s->len. + */ + if (atomic_cmpxchg(&s->len, len, len + add) != len) + goto again; + + /* Get flushed in a more safe context. */ + if (add) + irq_work_queue(&s->work); + + return add; +} + +/* + * printk one line from the temporary buffer from @start index until + * and including the @end index. + */ +static void print_nmi_seq_line(struct nmi_seq_buf *s, int start, int end) +{ + const char *buf = s->buffer + start; + + printk("%.*s", (end - start) + 1, buf); +} + +/* + * Flush data from the associated per_CPU buffer. The function + * can be called either via IRQ work or independently. + */ +static void __printk_nmi_flush(struct irq_work *work) +{ + static raw_spinlock_t read_lock = + __RAW_SPIN_LOCK_INITIALIZER(read_lock); + struct nmi_seq_buf *s = container_of(work, struct nmi_seq_buf, work); + int len, size, i, last_i; + + /* + * The lock has two functions. First, one reader has to flush all + * available message to make the lockless synchronization with + * writers easier. Second, we do not want to mix messages from + * different CPUs. This is especially important when printing + * a backtrace. + */ + raw_spin_lock(&read_lock); + + i = 0; +more: + len = atomic_read(&s->len); + + /* + * This is just a paranoid check that nobody has manipulated + * the buffer an unexpected way. If we printed something then + * @len must only increase. + */ + WARN_ON(i && i >= len); + + if (!len) + goto out; /* Someone else has already flushed the buffer. */ + + /* Make sure that data has been written up to the @len */ + smp_rmb(); + + size = min_t(int, len, sizeof(s->buffer)); + last_i = i; + + /* Print line by line. */ + for (; i < size; i++) { + if (s->buffer[i] == '\n') { + print_nmi_seq_line(s, last_i, i); + last_i = i + 1; + } + } + /* Check if there was a partial line. */ + if (last_i < size) { + print_nmi_seq_line(s, last_i, size - 1); + pr_cont("\n"); + } + + /* + * Check that nothing has got added in the meantime and truncate + * the buffer. Note that atomic_cmpxchg() is an implicit memory + * barrier that makes sure that the data were copied before + * updating s->len. + */ + if (atomic_cmpxchg(&s->len, len, 0) != len) + goto more; + +out: + raw_spin_unlock(&read_lock); +} + +/** + * printk_nmi_flush - flush all per-cpu nmi buffers. + * + * The buffers are flushed automatically via IRQ work. This function + * is useful only when someone wants to be sure that all buffers have + * been flushed at some point. + */ +void printk_nmi_flush(void) +{ + int cpu; + + for_each_possible_cpu(cpu) + __printk_nmi_flush(&per_cpu(nmi_print_seq, cpu).work); +} + +void __init printk_nmi_init(void) +{ + int cpu; + + for_each_possible_cpu(cpu) { + struct nmi_seq_buf *s = &per_cpu(nmi_print_seq, cpu); + + init_irq_work(&s->work, __printk_nmi_flush); + } +} + +void printk_nmi_enter(void) +{ + this_cpu_write(printk_func, vprintk_nmi); +} + +void printk_nmi_exit(void) +{ + this_cpu_write(printk_func, vprintk_default); +} diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 2ce8826f1053..88641c74163d 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -54,6 +54,7 @@ #include "console_cmdline.h" #include "braille.h" +#include "printk.h" int console_printk[4] = { CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */ @@ -1867,14 +1868,6 @@ int vprintk_default(const char *fmt, va_list args) } EXPORT_SYMBOL_GPL(vprintk_default); -/* - * This allows printk to be diverted to another function per cpu. - * This is useful for calling printk functions from within NMI - * without worrying about race conditions that can lock up the - * box. - */ -DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default; - /** * printk - print a kernel message * @fmt: format string @@ -1898,21 +1891,11 @@ DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default; */ asmlinkage __visible int printk(const char *fmt, ...) { - printk_func_t vprintk_func; va_list args; int r; va_start(args, fmt); - - /* - * If a caller overrides the per_cpu printk_func, then it needs - * to disable preemption when calling printk(). Otherwise - * the printk_func should be set to the default. No need to - * disable preemption here. - */ - vprintk_func = this_cpu_read(printk_func); r = vprintk_func(fmt, args); - va_end(args); return r; diff --git a/kernel/printk/printk.h b/kernel/printk/printk.h new file mode 100644 index 000000000000..3492f5def4ef --- /dev/null +++ b/kernel/printk/printk.h @@ -0,0 +1,44 @@ +/* + * printk.h - printk internal definitions + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ +#include <linux/percpu-defs.h> + +typedef __printf(1, 0) int (*printk_func_t)(const char *fmt, va_list args); + +int __printf(1, 0) vprintk_default(const char *fmt, va_list args); + +#ifdef CONFIG_PRINTK_NMI + +/* + * printk() could not take logbuf_lock in NMI context. Instead, + * it temporary stores the strings into a per-CPU buffer. + * The alternative implementation is chosen transparently + * via per-CPU variable. + */ +DECLARE_PER_CPU(printk_func_t, printk_func); +static inline __printf(1, 0) int vprintk_func(const char *fmt, va_list args) +{ + return this_cpu_read(printk_func)(fmt, args); +} + +#else /* CONFIG_PRINTK_NMI */ + +static inline __printf(1, 0) int vprintk_func(const char *fmt, va_list args) +{ + return vprintk_default(fmt, args); +} + +#endif /* CONFIG_PRINTK_NMI */ diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c index 6019c53c669e..26caf51cc238 100644 --- a/lib/nmi_backtrace.c +++ b/lib/nmi_backtrace.c @@ -16,33 +16,14 @@ #include <linux/delay.h> #include <linux/kprobes.h> #include <linux/nmi.h> -#include <linux/seq_buf.h> #ifdef arch_trigger_all_cpu_backtrace /* For reliability, we're prepared to waste bits here. */ static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; -static cpumask_t printtrace_mask; - -#define NMI_BUF_SIZE 4096 - -struct nmi_seq_buf { - unsigned char buffer[NMI_BUF_SIZE]; - struct seq_buf seq; -}; - -/* Safe printing in NMI context */ -static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq); /* "in progress" flag of arch_trigger_all_cpu_backtrace */ static unsigned long backtrace_flag; -static void print_seq_line(struct nmi_seq_buf *s, int start, int end) -{ - const char *buf = s->buffer + start; - - printk("%.*s", (end - start) + 1, buf); -} - /* * When raise() is called it will be is passed a pointer to the * backtrace_mask. Architectures that call nmi_cpu_backtrace() @@ -52,8 +33,7 @@ static void print_seq_line(struct nmi_seq_buf *s, int start, int end) void nmi_trigger_all_cpu_backtrace(bool include_self, void (*raise)(cpumask_t *mask)) { - struct nmi_seq_buf *s; - int i, cpu, this_cpu = get_cpu(); + int i, this_cpu = get_cpu(); if (test_and_set_bit(0, &backtrace_flag)) { /* @@ -68,17 +48,6 @@ void nmi_trigger_all_cpu_backtrace(bool include_self, if (!include_self) cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask)); - cpumask_copy(&printtrace_mask, to_cpumask(backtrace_mask)); - - /* - * Set up per_cpu seq_buf buffers that the NMIs running on the other - * CPUs will write to. - */ - for_each_cpu(cpu, to_cpumask(backtrace_mask)) { - s = &per_cpu(nmi_print_seq, cpu); - seq_buf_init(&s->seq, s->buffer, NMI_BUF_SIZE); - } - if (!cpumask_empty(to_cpumask(backtrace_mask))) { pr_info("Sending NMI to %s CPUs:\n", (include_self ? "all" : "other")); @@ -94,73 +63,25 @@ void nmi_trigger_all_cpu_backtrace(bool include_self, } /* - * Now that all the NMIs have triggered, we can dump out their - * back traces safely to the console. + * Force flush any remote buffers that might be stuck in IRQ context + * and therefore could not run their irq_work. */ - for_each_cpu(cpu, &printtrace_mask) { - int len, last_i = 0; + printk_nmi_flush(); - s = &per_cpu(nmi_print_seq, cpu); - len = seq_buf_used(&s->seq); - if (!len) - continue; - - /* Print line by line. */ - for (i = 0; i < len; i++) { - if (s->buffer[i] == '\n') { - print_seq_line(s, last_i, i); - last_i = i + 1; - } - } - /* Check if there was a partial line. */ - if (last_i < len) { - print_seq_line(s, last_i, len - 1); - pr_cont("\n"); - } - } - - clear_bit(0, &backtrace_flag); - smp_mb__after_atomic(); + clear_bit_unlock(0, &backtrace_flag); put_cpu(); } -/* - * It is not safe to call printk() directly from NMI handlers. - * It may be fine if the NMI detected a lock up and we have no choice - * but to do so, but doing a NMI on all other CPUs to get a back trace - * can be done with a sysrq-l. We don't want that to lock up, which - * can happen if the NMI interrupts a printk in progress. - * - * Instead, we redirect the vprintk() to this nmi_vprintk() that writes - * the content into a per cpu seq_buf buffer. Then when the NMIs are - * all done, we can safely dump the contents of the seq_buf to a printk() - * from a non NMI context. - */ -static int nmi_vprintk(const char *fmt, va_list args) -{ - struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq); - unsigned int len = seq_buf_used(&s->seq); - - seq_buf_vprintf(&s->seq, fmt, args); - return seq_buf_used(&s->seq) - len; -} - bool nmi_cpu_backtrace(struct pt_regs *regs) { int cpu = smp_processor_id(); if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { - printk_func_t printk_func_save = this_cpu_read(printk_func); - - /* Replace printk to write into the NMI seq */ - this_cpu_write(printk_func, nmi_vprintk); pr_warn("NMI backtrace for cpu %d\n", cpu); if (regs) show_regs(regs); else dump_stack(); - this_cpu_write(printk_func, printk_func_save); - cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask)); return true; }
printk() takes some locks and could not be used a safe way in NMI context. The chance of a deadlock is real especially when printing stacks from all CPUs. This particular problem has been addressed on x86 by the commit a9edc8809328 ("x86/nmi: Perform a safe NMI stack trace on all CPUs"). This patch reuses most of the code and makes it generic. It is useful for all messages and architectures that support NMI. The alternative printk_func is set when entering and is reseted when leaving NMI context. It queues IRQ work to copy the messages into the main ring buffer in a safe context. __printk_nmi_flush() copies all available messages and reset the buffer. Then we could use a simple cmpxchg operations to get synchronized with writers. There is also used a spinlock to get synchronized with other flushers. We do not longer use seq_buf because it depends on external lock. It would be hard to make all supported operations safe for a lockless use. It would be confusing and error prone to make only some operations safe. The code is put into separate printk/nmi.c as suggested by Steven Rostedt. It needs a per-CPU buffer and is compiled only on architectures that call nmi_enter(). This is achieved by the new HAVE_NMI Kconfig flag. One exception is arm where the deferred printing is used for printing backtraces even without NMI. For this purpose, we define NEED_PRINTK_NMI Kconfig flag. The alternative printk_func is explicitly set when IPI_CPU_BACKTRACE is handled. Another exception is Xtensa architecture that uses just a fake NMI. The patch is heavily based on the draft from Peter Zijlstra, see https://lkml.org/lkml/2015/6/10/327 Suggested-by: Peter Zijlstra <peterz@infradead.org> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Petr Mladek <pmladek@suse.com> --- arch/Kconfig | 7 ++ arch/arm/Kconfig | 2 + arch/arm/kernel/smp.c | 2 + arch/avr32/Kconfig | 1 + arch/blackfin/Kconfig | 1 + arch/cris/Kconfig | 1 + arch/mips/Kconfig | 1 + arch/powerpc/Kconfig | 1 + arch/s390/Kconfig | 1 + arch/sh/Kconfig | 1 + arch/sparc/Kconfig | 1 + arch/tile/Kconfig | 1 + arch/x86/Kconfig | 1 + arch/x86/kernel/apic/hw_nmi.c | 1 - include/linux/hardirq.h | 2 + include/linux/percpu.h | 3 - include/linux/printk.h | 12 ++- init/Kconfig | 5 ++ init/main.c | 1 + kernel/printk/Makefile | 1 + kernel/printk/nmi.c | 200 ++++++++++++++++++++++++++++++++++++++++++ kernel/printk/printk.c | 19 +--- kernel/printk/printk.h | 44 ++++++++++ lib/nmi_backtrace.c | 89 ++----------------- 24 files changed, 291 insertions(+), 107 deletions(-) create mode 100644 kernel/printk/nmi.c create mode 100644 kernel/printk/printk.h