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| author | Christian Krinitsin <mail@krinitsin.com> | 2025-06-30 12:34:26 +0000 |
|---|---|---|
| committer | Christian Krinitsin <mail@krinitsin.com> | 2025-06-30 12:35:44 +0000 |
| commit | 25f8033d556aa17afaea4a5196ea7a69fe248320 (patch) | |
| tree | 0f056db167683be54ea1e5e72d29d6069af55e7d /results/classifier/deepseek-2-tmp/output/kernel/1887306 | |
| parent | 8e6da29e4ee5fc14bc1cc816a24f21271f14090d (diff) | |
| download | emulator-bug-study-25f8033d556aa17afaea4a5196ea7a69fe248320.tar.gz emulator-bug-study-25f8033d556aa17afaea4a5196ea7a69fe248320.zip | |
add new temporary deepseek-r1:14b results
Diffstat (limited to 'results/classifier/deepseek-2-tmp/output/kernel/1887306')
| -rw-r--r-- | results/classifier/deepseek-2-tmp/output/kernel/1887306 | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/results/classifier/deepseek-2-tmp/output/kernel/1887306 b/results/classifier/deepseek-2-tmp/output/kernel/1887306 new file mode 100644 index 00000000..0ea9a50c --- /dev/null +++ b/results/classifier/deepseek-2-tmp/output/kernel/1887306 @@ -0,0 +1,56 @@ + +qemu-user deadlocks when forked in a multithreaded process + +The following program (also attached) deadlocks when run under QEMU user on Linux. + +#include <pthread.h> +#include <stdio.h> +#include <stdlib.h> +#include <sys/types.h> +#include <sys/wait.h> +#include <unistd.h> + +#define NUM_THREADS 100 +#define NUM_FORKS 10 + +pthread_barrier_t barrier; + +void *t(void *arg) { + for (int i = 0; i < NUM_FORKS; i++) { + pid_t pid = fork(); + if (pid < 0) + abort(); + if (!pid) + _exit(0); + if (waitpid(pid, NULL, 0) < 0) + abort(); + } + //pthread_barrier_wait(&barrier); + return NULL; +} + +int main(void) { + pthread_barrier_init(&barrier, NULL, NUM_THREADS); + pthread_t ts[NUM_THREADS]; + for (size_t i = 0; i < NUM_THREADS; i++) { + if (pthread_create(&ts[i], NULL, t, NULL)) + abort(); + } + for (size_t i = 0; i < NUM_THREADS; i++) { + pthread_join(ts[i], NULL); + } + printf("Done: %d\n", getpid()); + return 0; +} + +To reproduce: +$ gcc test.c -pthread +$ while qemu-x86_64 ./a.out; do :; done + +(Be careful, Ctrl-C/SIGINT doesn't kill the deadlocked child). + +Larger values of NUM_THREADS/NUM_FORKS lead to more often deadlocks. With the values above it often deadlocks on the first try on my machine. When it deadlocks, there is a child qemu process with two threads which is waited upon by one of the worker threads of the parent. + +I tried to avoid the deadlock by serializing fork() with a mutex, but it didn't help. However, ensuring that no thread exits until all forks are done (by adding a barrier to t()) does seem to help, at least, the program above could run for a half an hour until I terminated it. + +Tested on QEMU 5.0.0, 4.2.0 and 2.11.1, with x86_64 and AArch64 linux-user targets.
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