Messages in this thread |  | | From | Sasha Pachev <> | Subject | Test case for kernel crash | Date | Fri, 6 Jul 2001 18:30:32 -0600 |
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I am able to crash 2.4.3 kernel on a dual Pentium 500 with 256 MB RAM and no swap space with the program below. to compile, gcc -o oom oom.c -lpthread
Found out that my magic SysRq for some reason was not working :( so I could not get much detail - will fix the magic and report more when it becomes available. I have observed three types of behavior:
* once the program locked everything up ( test run from X), the machine did not even ping. However, after some time ( about 5 minutes), the machine became functional again * another time, there was a complete lockup ( again in X), I waited 10 minutes, nothing happened, so I just rebooted * then I tried the test after a clean boot - this time no X, just plain consoles - after the run I actually got the shell back, could not type anything. I could switch between virtual consoles, type my username at the login prompt, but would never get the password prompt. The machine pinged, and I could even connect to ports that had services, but got no response after a successfull connect. My explanation is that the kernel ran out of memory, but could not clean up.
The only relevant thing I could find in syslog is messages like this:
Jul 6 17:33:31 mysql kernel: Out of Memory: Killed process 25500 (oom). Jul 6 17:33:35 mysql last message repeated 84 times Jul 6 17:33:35 mysql kernel: Out of Memory: Killed process 25501 (oom). Jul 6 17:33:35 mysql last message repeated 5 times Jul 6 17:33:35 mysql kernel: Out of Memory: Killed process 25502 (oom). Jul 6 17:33:35 mysql last message repeated 263 times
And last but not least - the whole reason for writing the program below was to create a simple test case and isolate the problem in a real life threaded application that left some unkillable ( even with -9 ) processes after running out of memory and getting killed itself. So I suspect I have accomplished my goal of creating unkillable process, which is what, apparently, makes it so difficult for the kernel to recover from the stress.
Note that I had to get the process stuck in I/O to cause the problem - without the I/O the kernel kills all the bad guys and recovers gracefully.
So let's hope this is enough info to track down the bug - if not let me know what else is needed.
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#include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <unistd.h>
#define LEAK_BLOCK (1024*1024) #define MB (1024*1024) #define NUM_THREADS 64
int pipe_fd[2];
void* run_thread(void* arg) { unsigned long total = 0; char buf[3]; for (;;) { char* p, *p_end; if(!(p=malloc(LEAK_BLOCK))) { fprintf(stderr, "malloc() failed\n"); exit(1); } p_end = p + LEAK_BLOCK; while(p < p_end) *p++ = 0; total += LEAK_BLOCK; printf("Allocated %d MB\n", total/MB); fflush(stdout); read(pipe_fd[0], buf, 3); } return 0; }
int main() { pthread_t th[NUM_THREADS]; int i;
if(pipe(pipe_fd) == -1) { fprintf(stderr, "Could not create pipe\n"); exit(1); }
for(i = 0; i < NUM_THREADS; i++) if(pthread_create(th + i, 0, run_thread, 0)) { fprintf(stderr, "Could not create thread\n"); exit(1); }
while(1) { write(pipe_fd[1], "foo", 3); }
for(i = 0; i < NUM_THREADS; i++) if(pthread_join(th[i], 0)) { fprintf(stderr, "Error in pthread_join\n"); exit(1); } return 0; }
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-- MySQL Development Team For technical support contracts, visit https://order.mysql.com/ __ ___ ___ ____ __ / |/ /_ __/ __/ __ \/ / Sasha Pachev <sasha@mysql.com> / /|_/ / // /\ \/ /_/ / /__ MySQL AB, http://www.mysql.com/ /_/ /_/\_, /___/\___\_\___/ Provo, Utah, USA <___/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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