Re: [PATCH POC 2/4] printk: Do not block cont buffer by partially flushed lines

From: kbuild test robot
Date: Fri Jul 15 2016 - 14:27:31 EST

Hi,

[auto build test ERROR on v4.7-rc7]
[cannot apply to next-20160715]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Petr-Mladek/printk-Several-fixes-of-cont-buffer-and-console-handling/20160716-012724
config: i386-tinyconfig (attached as .config)
compiler: gcc-6 (Debian 6.1.1-1) 6.1.1 20160430
reproduce:
# save the attached .config to linux build tree
make ARCH=i386

All error/warnings (new ones prefixed by >>):

kernel/printk/printk.c: In function 'console_cont_flush':
kernel/printk/printk.c:2150:11: error: 'struct cont' has no member named 'msg'
if (!cont.msg->text_len)
^
>> kernel/printk/printk.c:2160:24: error: passing argument 1 of 'cont_print_text' from incompatible pointer type [-Werror=incompatible-pointer-types]
len = cont_print_text(&cont, text, size);
^
kernel/printk/printk.c:1873:15: note: expected 'char *' but argument is of type 'struct cont *'
static size_t cont_print_text(char *text, size_t size) { return 0; }
^~~~~~~~~~~~~~~
>> kernel/printk/printk.c:2160:31: warning: passing argument 2 of 'cont_print_text' makes integer from pointer without a cast [-Wint-conversion]
len = cont_print_text(&cont, text, size);
^~~~
kernel/printk/printk.c:1873:15: note: expected 'size_t {aka unsigned int}' but argument is of type 'char *'
static size_t cont_print_text(char *text, size_t size) { return 0; }
^~~~~~~~~~~~~~~
>> kernel/printk/printk.c:2160:8: error: too many arguments to function 'cont_print_text'
len = cont_print_text(&cont, text, size);
^~~~~~~~~~~~~~~
kernel/printk/printk.c:1873:15: note: declared here
static size_t cont_print_text(char *text, size_t size) { return 0; }
^~~~~~~~~~~~~~~
kernel/printk/printk.c:2163:27: error: 'struct cont' has no member named 'msg'
call_console_drivers(cont.msg->level, NULL, 0, text, len);
^
kernel/printk/printk.c: In function 'console_unlock':
kernel/printk/printk.c:2262:7: error: 'cont_console_len' undeclared (first use in this function)
if (cont_console_len && cont_console_seq == console_seq) {
^~~~~~~~~~~~~~~~
kernel/printk/printk.c:2262:7: note: each undeclared identifier is reported only once for each function it appears in
>> kernel/printk/printk.c:2262:27: error: 'cont_console_seq' undeclared (first use in this function)
if (cont_console_len && cont_console_seq == console_seq) {
^~~~~~~~~~~~~~~~
>> kernel/printk/printk.c:2265:13: error: 'struct cont' has no member named 'owner'
fake_cont.owner = NULL;
^
kernel/printk/printk.c:2266:13: error: 'struct cont' has no member named 'msg'
fake_cont.msg = msg;
^
>> kernel/printk/printk.c:2267:13: error: 'struct cont' has no member named 'buf'
fake_cont.buf = log_text(msg);
^
kernel/printk/printk.c:2269:27: error: passing argument 1 of 'cont_print_text' from incompatible pointer type [-Werror=incompatible-pointer-types]
len += cont_print_text(&fake_cont, text + len, sizeof(text) - len);
^
kernel/printk/printk.c:1873:15: note: expected 'char *' but argument is of type 'struct cont *'
static size_t cont_print_text(char *text, size_t size) { return 0; }
^~~~~~~~~~~~~~~
kernel/printk/printk.c:2269:39: warning: passing argument 2 of 'cont_print_text' makes integer from pointer without a cast [-Wint-conversion]
len += cont_print_text(&fake_cont, text + len, sizeof(text) - len);
^~~~
kernel/printk/printk.c:1873:15: note: expected 'size_t {aka unsigned int}' but argument is of type 'char *'
static size_t cont_print_text(char *text, size_t size) { return 0; }
^~~~~~~~~~~~~~~
kernel/printk/printk.c:2269:11: error: too many arguments to function 'cont_print_text'
len += cont_print_text(&fake_cont, text + len, sizeof(text) - len);
^~~~~~~~~~~~~~~
kernel/printk/printk.c:1873:15: note: declared here
static size_t cont_print_text(char *text, size_t size) { return 0; }
^~~~~~~~~~~~~~~
cc1: some warnings being treated as errors

vim +/cont_print_text +2160 kernel/printk/printk.c

2144 {
2145 unsigned long flags;
2146 size_t len;
2147
2148 raw_spin_lock_irqsave(&logbuf_lock, flags);
2149
> 2150 if (!cont.msg->text_len)
2151 goto out;
2152
2153 /*
2154 * If the partially printed line is already stored in
2155 * the ring buffer, it will be handled with the other lines.
2156 */
2157 if (console_seq < log_next_seq)
2158 goto out;
2159
> 2160 len = cont_print_text(&cont, text, size);
2161 raw_spin_unlock(&logbuf_lock);
2162 stop_critical_timings();
> 2163 call_console_drivers(cont.msg->level, NULL, 0, text, len);
2164 start_critical_timings();
2165 local_irq_restore(flags);
2166 return;
2167 out:
2168 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2169 }
2170
2171 /**
2172 * console_unlock - unlock the console system
2173 *
2174 * Releases the console_lock which the caller holds on the console system
2175 * and the console driver list.
2176 *
2177 * While the console_lock was held, console output may have been buffered
2178 * by printk(). If this is the case, console_unlock(); emits
2179 * the output prior to releasing the lock.
2180 *
2181 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2182 *
2183 * console_unlock(); may be called from any context.
2184 */
2185 void console_unlock(void)
2186 {
2187 static char ext_text[CONSOLE_EXT_LOG_MAX];
2188 static char text[LOG_LINE_MAX + PREFIX_MAX];
2189 static u64 seen_seq;
2190 unsigned long flags;
2191 bool wake_klogd = false;
2192 bool do_cond_resched, retry;
2193
2194 if (console_suspended) {
2195 up_console_sem();
2196 return;
2197 }
2198
2199 /*
2200 * Console drivers are called under logbuf_lock, so
2201 * @console_may_schedule should be cleared before; however, we may
2202 * end up dumping a lot of lines, for example, if called from
2203 * console registration path, and should invoke cond_resched()
2204 * between lines if allowable. Not doing so can cause a very long
2205 * scheduling stall on a slow console leading to RCU stall and
2206 * softlockup warnings which exacerbate the issue with more
2207 * messages practically incapacitating the system.
2208 */
2209 do_cond_resched = console_may_schedule;
2210 console_may_schedule = 0;
2211
2212 again:
2213 /*
2214 * We released the console_sem lock, so we need to recheck if
2215 * cpu is online and (if not) is there at least one CON_ANYTIME
2216 * console.
2217 */
2218 if (!can_use_console()) {
2219 console_locked = 0;
2220 up_console_sem();
2221 return;
2222 }
2223
2224 /* flush buffered message fragment immediately to console */
2225 console_cont_flush(text, sizeof(text));
2226
2227 for (;;) {
2228 struct printk_log *msg;
2229 size_t ext_len = 0;
2230 size_t len;
2231 int level;
2232
2233 raw_spin_lock_irqsave(&logbuf_lock, flags);
2234 if (seen_seq != log_next_seq) {
2235 wake_klogd = true;
2236 seen_seq = log_next_seq;
2237 }
2238
2239 if (console_seq < log_first_seq) {
2240 len = sprintf(text, "** %u printk messages dropped ** ",
2241 (unsigned)(log_first_seq - console_seq));
2242
2243 /* messages are gone, move to first one */
2244 console_seq = log_first_seq;
2245 console_idx = log_first_idx;
2246 console_prev = 0;
2247 } else {
2248 len = 0;
2249 }
2250
2251 if (console_seq == log_next_seq)
2252 break;
2253
2254 msg = log_from_idx(console_idx);
2255 level = msg->level;
2256
2257 /*
2258 * The line might be already partially printed from the cont
2259 * buffer. In this case, flush the rest using a fake
2260 * cont buffer.
2261 */
> 2262 if (cont_console_len && cont_console_seq == console_seq) {
2263 struct cont fake_cont;
2264
> 2265 fake_cont.owner = NULL;
2266 fake_cont.msg = msg;
> 2267 fake_cont.buf = log_text(msg);
2268
2269 len += cont_print_text(&fake_cont, text + len, sizeof(text) - len);
2270

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