On x86, do_signal() leaves -516 in eax while it freezes, which
sys_restart() can use to detect that it should restart the
syscall which was interrupted by a signal (or the freezer).
On s390, gprs[2] gets tweaked to -EINTR (-4) instead, leaving
us no reliable way to tell whether should be restarted.
Define TIF_RESTARTBLOCK as a thread flag showing that the
thread expects to be frozen while kicked out of a restartable
syscall by a signal.
This is needed so that, if it is checkpointed and restarted,
the restarted task has a way to tell that, upon completion
of sys_restart(), it should restart the interrupted syscall.
Without this patch, restart of the program
close(0); close(1); close(2);
sleep(30);
immediately exits. With the patch, it continues to sleep for
the remaining sleep time.
Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx>
---
arch/s390/include/asm/checkpoint_hdr.h | 1 +
arch/s390/include/asm/thread_info.h | 2 ++
arch/s390/kernel/signal.c | 3 +++
arch/s390/mm/checkpoint.c | 16 ++++++++++++++++
4 files changed, 22 insertions(+), 0 deletions(-)
diff --git a/arch/s390/include/asm/checkpoint_hdr.h b/arch/s390/include/asm/checkpoint_hdr.h
index bc9f624..4ef14e8 100644
--- a/arch/s390/include/asm/checkpoint_hdr.h
+++ b/arch/s390/include/asm/checkpoint_hdr.h
@@ -73,6 +73,7 @@ struct ckpt_hdr_cpu {
__u8 access_id;
__u8 single_step;
__u8 instruction_fetch;
+ __u8 should_restart;
};
struct ckpt_hdr_mm_context {
diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h
index 07eb61b..2fac866 100644
--- a/arch/s390/include/asm/thread_info.h
+++ b/arch/s390/include/asm/thread_info.h
@@ -100,6 +100,7 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_MEMDIE 19
#define TIF_RESTORE_SIGMASK 20 /* restore signal mask in do_signal() */
#define TIF_FREEZE 21 /* thread is freezing for suspend */
+#define TIF_RESTARTBLOCK 23 /* for checkpoint */
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
@@ -116,6 +117,7 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_31BIT (1<<TIF_31BIT)
#define _TIF_FREEZE (1<<TIF_FREEZE)
+#define _TIF_RESTARTBLOCK (1<<TIF_RESTARTBLOCK)
#endif /* __KERNEL__ */
diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index 6b4fef8..1179b19 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -458,6 +458,7 @@ void do_signal(struct pt_regs *regs)
regs->psw.addr = restart_addr;
break;
case -ERESTART_RESTARTBLOCK:
+ set_thread_flag(TIF_RESTARTBLOCK);
regs->gprs[2] = -EINTR;
}
regs->svcnr = 0; /* Don't deal with this again. */
@@ -467,6 +468,8 @@ void do_signal(struct pt_regs *regs)
the debugger may change all our registers ... */
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
+ clear_thread_flag(TIF_RESTARTBLOCK);
+
/* Depending on the signal settings we may need to revert the
decision to restart the system call. */
if (signr > 0 && regs->psw.addr == restart_addr) {
diff --git a/arch/s390/mm/checkpoint.c b/arch/s390/mm/checkpoint.c
index 40dd417..d8d4b6b 100644
--- a/arch/s390/mm/checkpoint.c
+++ b/arch/s390/mm/checkpoint.c
@@ -65,6 +65,16 @@ static void s390_copy_regs(int op, struct ckpt_hdr_cpu *h,
BUG_ON(h->gprs[2] < 0);
h->gprs[2] = 0;
}
+ /*
+ * if the checkpointed task was frozen in a syscall with
+ * -ERESTART_RESTARTBLOCK (switched to -EINTR during do_signal()
+ * before try_to_freeze() happened) * then after restart we need
+ * to call __NR_restart_syscall to continue. Fix up here.
+ */
+ if (op == CKPT_RST && h->should_restart) {
+ regs->gprs[2] = __NR_restart_syscall;
+ set_thread_flag(TIF_RESTART_SVC);
+ }
CKPT_COPY_ARRAY(op, h->fprs, thr->fp_regs.fprs, NUM_FPRS);
CKPT_COPY_ARRAY(op, h->acrs, thr->acrs, NUM_ACRS);
CKPT_COPY_ARRAY(op, h->per_control_regs,
@@ -98,6 +108,12 @@ int checkpoint_cpu(struct ckpt_ctx *ctx, struct task_struct *t)
s390_copy_regs(CKPT_CPT, h, t);
+ /*
+ * if t was frozen while in a restartable syscall, note that
+ */
+ if (test_ti_thread_flag(task_thread_info(t), TIF_RESTARTBLOCK))
+ h->should_restart = 1;
+
ret = ckpt_write_obj(ctx, (struct ckpt_hdr *) h);
ckpt_hdr_put(ctx, h);
--
1.6.1
_______________________________________________
Containers mailing list
Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linux-foundation.org/mailman/listinfo/containers
