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Subject: debug with kgdb,why not work? - msg#00007List: linux.kernel.debugging.kgdb.bugsFor days, I am searching for a way to look inside the linux kernel for studying it. I have tried kdb,kgdb and user-mode-linux, and think kgdb is better. All I have setup for kgdb,the target machine waiting for remote connection, the develep machine connecs to it, and control the target. All things look good. But when I setup breakpoints in linux-2.4.23/mm/vmscan.c:820, that is ,the place kswapd()->kswapd_balance(),and let target continue running, I can't see target stop at this breakpoint. As I know, kswap is a background and will invoke from time to time. I use "thread 5" to switch to kswapd and still doesn't work. Is it any matter with multi-processes or muti-threads? I know little about gdb debugging muti-programming. But as I tried UML(user mode linux), the kswap can easily hit the breakpoint. but uml modifies kernel code too much, I don't like it very much ... I have read many from the linsyssoft.com but can' find an answer. Any hints from you are very very appreciated. Thanks. ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_idv37&alloc_id865&op=click Thread at a glance:
Next Message by Date: click to view message previewRe: debug with kgdb,why not work?èèè, vmscan.c:820 contains a call to kswapd_balance, which is defined as a static function earlier (line 725). Gcc will expand this call inline. The call to remove_wait_queue is also expanded inline since remove_wait_queue is defined as a static inline function. 811 812 __set_current_state(TASK_RUNNING); 813 remove_wait_queue(&kswapd_wait, &wait); 814 815 /* 816 * If we actually get into a low-memory situation, 817 * the processes needing more memory will wake us 818 * up on a more timely basis. 819 */ 820 kswapd_balance(); 821 run_task_queue(&tq_disk); 822 } 823 } 824 At present gcc or gdb respectively can't generate and handle inline functions as good as they do real functions. You'll see line nos correctly but not all the symbol information. You may try placing a breakpoint inside kswapd_balance, line no. 731, which is a simple C statement. 725 static void kswapd_balance(void) 726 { 727 int need_more_balance; 728 pg_data_t * pgdat; 729 730 do { 731 need_more_balance = 0; 732 info threads should work fine. "thread 5" will not switch threads in the kernel. It'll only ask gdb to use thread 5 for further commands like backtrace. A backtrace command after a "thread 5" command (assuming that the kswapd is thread number 5) will show you the backtrace kswapd at the state where it's sleeping or is running on another processor. -- Amit Kale LinSysSoft Technologies Ask me about KGDB Pro http://www.linsyssoft.com/Kgdbpro.html On Monday 05 Dec 2005 10:54 am, èèè wrote: > Hi, all. > > For days, I am searching for a way to look inside the linux kernel > for studying it. I have tried kdb,kgdb and user-mode-linux, and think > kgdb is better. All I have setup for kgdb,the target machine waiting > for remote connection, the develep machine connecs to it, and control > the target. All things look good. But when I setup breakpoints in > linux-2.4.23/mm/vmscan.c:820, that is ,the place > kswapd()->kswapd_balance(),and let target continue running, I can't > see target stop at this breakpoint. As I know, kswap is a background > and will invoke from time to time. I use "thread 5" to switch to > kswapd and still doesn't work. Is it any matter with multi-processes > or muti-threads? I know little about gdb debugging muti-programming. > But as I tried UML(user mode linux), the kswap can easily hit the > breakpoint. but uml modifies kernel code too much, I don't like it > very much ... > I have read many from the linsyssoft.com but can' find an answer. > Any hints from you are very very appreciated. > Thanks. > > > ------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. Do you grep through log > files for problems? Stop! Download the new AJAX search engine that makes > searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! > http://ads.osdn.com/?ad_idv37&alloc_id865&op=Click > _______________________________________________ > Kgdb-bugreport mailing list > Kgdb-bugreport@xxxxxxxxxxxxxxxxxxxxx > https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_idv37&alloc_id865&op=click Next Message by Thread: click to view message previewRe: debug with kgdb,why not work?èèè, vmscan.c:820 contains a call to kswapd_balance, which is defined as a static function earlier (line 725). Gcc will expand this call inline. The call to remove_wait_queue is also expanded inline since remove_wait_queue is defined as a static inline function. 811 812 __set_current_state(TASK_RUNNING); 813 remove_wait_queue(&kswapd_wait, &wait); 814 815 /* 816 * If we actually get into a low-memory situation, 817 * the processes needing more memory will wake us 818 * up on a more timely basis. 819 */ 820 kswapd_balance(); 821 run_task_queue(&tq_disk); 822 } 823 } 824 At present gcc or gdb respectively can't generate and handle inline functions as good as they do real functions. You'll see line nos correctly but not all the symbol information. You may try placing a breakpoint inside kswapd_balance, line no. 731, which is a simple C statement. 725 static void kswapd_balance(void) 726 { 727 int need_more_balance; 728 pg_data_t * pgdat; 729 730 do { 731 need_more_balance = 0; 732 info threads should work fine. "thread 5" will not switch threads in the kernel. It'll only ask gdb to use thread 5 for further commands like backtrace. A backtrace command after a "thread 5" command (assuming that the kswapd is thread number 5) will show you the backtrace kswapd at the state where it's sleeping or is running on another processor. -- Amit Kale LinSysSoft Technologies Ask me about KGDB Pro http://www.linsyssoft.com/Kgdbpro.html On Monday 05 Dec 2005 10:54 am, èèè wrote: > Hi, all. > > For days, I am searching for a way to look inside the linux kernel > for studying it. I have tried kdb,kgdb and user-mode-linux, and think > kgdb is better. All I have setup for kgdb,the target machine waiting > for remote connection, the develep machine connecs to it, and control > the target. All things look good. But when I setup breakpoints in > linux-2.4.23/mm/vmscan.c:820, that is ,the place > kswapd()->kswapd_balance(),and let target continue running, I can't > see target stop at this breakpoint. As I know, kswap is a background > and will invoke from time to time. I use "thread 5" to switch to > kswapd and still doesn't work. Is it any matter with multi-processes > or muti-threads? I know little about gdb debugging muti-programming. > But as I tried UML(user mode linux), the kswap can easily hit the > breakpoint. but uml modifies kernel code too much, I don't like it > very much ... > I have read many from the linsyssoft.com but can' find an answer. > Any hints from you are very very appreciated. > Thanks. > > > ------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. Do you grep through log > files for problems? Stop! Download the new AJAX search engine that makes > searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! > http://ads.osdn.com/?ad_idv37&alloc_id865&op=Click > _______________________________________________ > Kgdb-bugreport mailing list > Kgdb-bugreport@xxxxxxxxxxxxxxxxxxxxx > https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_idv37&alloc_id865&op=click Loading Comments...
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