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authorSuresh Siddha <suresh.b.siddha@intel.com>2012-05-16 15:03:52 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2012-05-16 15:16:48 -0700
commit11aeca0b3a083a457f5c34fe8c677d5e86a0c6b3 (patch)
tree8d71ab524aa13aa8fd2bf10d7bbf3ddfa89ac4f7 /fs/exec.c
parent55ccf3fe3f9a3441731aa79cf42a628fc4ecace9 (diff)
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coredump: ensure the fpu state is flushed for proper multi-threaded core dump
Nalluru reported hitting the BUG_ON(__thread_has_fpu(tsk)) in arch/x86/kernel/xsave.c:__sanitize_i387_state() during the coredump of a multi-threaded application. A look at the exit seqeuence shows that other threads can still be on the runqueue potentially at the below shown exit_mm() code snippet: if (atomic_dec_and_test(&core_state->nr_threads)) complete(&core_state->startup); ===> other threads can still be active here, but we notify the thread ===> dumping core to wakeup from the coredump_wait() after the last thread ===> joins this point. Core dumping thread will continue dumping ===> all the threads state to the core file. for (;;) { set_task_state(tsk, TASK_UNINTERRUPTIBLE); if (!self.task) /* see coredump_finish() */ break; schedule(); } As some of those threads are on the runqueue and didn't call schedule() yet, their fpu state is still active in the live registers and the thread proceeding with the coredump will hit the above mentioned BUG_ON while trying to dump other threads fpustate to the coredump file. BUG_ON() in arch/x86/kernel/xsave.c:__sanitize_i387_state() is in the code paths for processors supporting xsaveopt. With or without xsaveopt, multi-threaded coredump is broken and maynot contain the correct fpustate at the time of exit. In coredump_wait(), wait for all the threads to be come inactive, so that we are sure all the extended register state is flushed to the memory, so that it can be reliably copied to the core file. Reported-by: Suresh Nalluru <suresh@aristanetworks.com> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Link: http://lkml.kernel.org/r/1336692811-30576-2-git-send-email-suresh.b.siddha@intel.com Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'fs/exec.c')
-rw-r--r--fs/exec.c15
1 files changed, 14 insertions, 1 deletions
diff --git a/fs/exec.c b/fs/exec.c
index b1fd2025e59..8e2ddebaccd 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1930,8 +1930,21 @@ static int coredump_wait(int exit_code, struct core_state *core_state)
core_waiters = zap_threads(tsk, mm, core_state, exit_code);
up_write(&mm->mmap_sem);
- if (core_waiters > 0)
+ if (core_waiters > 0) {
+ struct core_thread *ptr;
+
wait_for_completion(&core_state->startup);
+ /*
+ * Wait for all the threads to become inactive, so that
+ * all the thread context (extended register state, like
+ * fpu etc) gets copied to the memory.
+ */
+ ptr = core_state->dumper.next;
+ while (ptr != NULL) {
+ wait_task_inactive(ptr->task, 0);
+ ptr = ptr->next;
+ }
+ }
return core_waiters;
}