(This is a patch against the checkpoint/restart kernel tree at http://git.ncl.cs.columbia.edu/?p=linux-cr.git;a=shortlog;h=refs/heads/ckpt-v19-rc2.9) 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. If the task is checkpointed here and then restarted, then the last part of do_signal() won't be done, and the interrupted syscall won't be restarted. This patch defines TIF_RESTARTBLOCK as a thread flag showing that the thread expects to be frozen while kicked out of a restartable syscall by a signal. The TIF_RESTARTBLOCK flag is only set for the duration of the get get_signal_to_deliver() which is where the task may get frozen. We also set it in sys_restart() if the checkpointed task had had TIF_RESTARTBLOCK set. It will get cleared if upon exiting sys_restart() we jump to sysc_sigpending. If instead we jump back to do_signal(), then TIF_RESTARTBLOCK will stay set again until after get_signal_to_deliver() so that if it immediately freezes and is re-checkpointed, the resulting second checkpoint image again will have TIF_RESTARTBLOCK set. To test this, add a dummy handler for SIGUSR1 to cr_tests/sleep/sleeptest.c, open two terminals, and do: Terminal 1: Terminal : mount -t cgroup -o freezer freezer /cgroup mkdir /cgroup/1 /cgroup/2 echo $$ > /cgroup/1/tasks ./sleeptest echo FROZEN > /cgroup/1/freezer.state checkpoint `pidof sleeptest` > /tmp/out thaw restart -F /cgroup/2 < /tmp/out kill -USR1 `pidof sleeptest`; echo THAWED > /cgroup/2/freezer.state ; sleep 0.3; echo FROZEN > /cgroup/2/freezer.state; checkpoint `pidof sleeptest` > /tmp/out2; echo THAWED > /cgroup/2/freezer.state restart < /tmp/out2 Without this patch, the first restart will immediately exit. Without re-setting TIF_RESTARTBLOCK in sys_restart(), the second restart will immediately exit. With this full patch, it will restart the sleep correctly. Cc: linux-s390@xxxxxxxxxxxxxxx Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx> --- arch/s390/include/asm/checkpoint_hdr.h | 5 +++ arch/s390/include/asm/thread_info.h | 2 + arch/s390/kernel/checkpoint.c | 52 +++++++++++++++++++++++++++++++- arch/s390/kernel/entry64.S | 2 + arch/s390/kernel/signal.c | 6 ++++ 5 files changed, 66 insertions(+), 1 deletions(-) diff --git a/arch/s390/include/asm/checkpoint_hdr.h b/arch/s390/include/asm/checkpoint_hdr.h index a8c2a3d..fd8be2a 100644 --- a/arch/s390/include/asm/checkpoint_hdr.h +++ b/arch/s390/include/asm/checkpoint_hdr.h @@ -76,6 +76,11 @@ struct ckpt_hdr_cpu { __u8 instruction_fetch; }; +struct ckpt_hdr_thread { + struct ckpt_hdr h; + __u64 thread_info_flags; +}; + struct ckpt_hdr_mm_context { struct ckpt_hdr h; unsigned long vdso_base; diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h index 07eb61b..6ef11b2 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 /* use restart block after sys_restart */ #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/checkpoint.c b/arch/s390/kernel/checkpoint.c index 60ba04d..092fd87 100644 --- a/arch/s390/kernel/checkpoint.c +++ b/arch/s390/kernel/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 checkpoint was taken while interrupted from restartable + * system call, then restore_thread() will have already reset + * TIF_RESTARTBLOCK, but it did not set gprs[2]. It's easier to + * do that here where gprs registers are all restored. + */ + if (op == CKPT_RST && test_thread_flag(TIF_RESTARTBLOCK)) + regs->gprs[2] = __NR_restart_syscall; + 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, @@ -83,12 +93,24 @@ static void s390_mm(int op, struct ckpt_hdr_mm_context *h, int checkpoint_thread(struct ckpt_ctx *ctx, struct task_struct *t) { + struct ckpt_hdr_thread *h; + int ret; + /* we will eventually support this, as we do on x86-64 */ if (test_tsk_thread_flag(t, TIF_31BIT)) { ckpt_err(ctx, -EINVAL, "checkpoint of 31-bit task\n"); return -EINVAL; } - return 0; + + h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_THREAD); + if (!h) + return -ENOMEM; + + h->thread_info_flags = task_thread_info(t)->flags; + ret = ckpt_write_obj(ctx, &h->h); + ckpt_hdr_put(ctx, h); + + return ret; } /* dump the cpu state and registers of a given task */ @@ -148,11 +170,39 @@ int checkpoint_mm_context(struct ckpt_ctx *ctx, struct mm_struct *mm) int restore_thread(struct ckpt_ctx *ctx) { + struct ckpt_hdr_thread *h; + /* a 31-bit task cannot call sys_restart right now */ if (test_thread_flag(TIF_31BIT)) { ckpt_err(ctx, -EINVAL, "restart from 31-bit task\n"); return -EINVAL; } + + h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_THREAD); + if (IS_ERR(h)) + return PTR_ERR(h); + + /* + * 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. + * In other words, we're doing the rest of the fixup which the + * end of do_signal(), which won't now be run, would have done. + * + * We also re-set TIF_RESTARTBLOCK in case we hit do_signal + * right after sys_restart() instead of sysc_restart, since + * we would enter do_signal() with different inital conditions + * than usual for being "inside" a restartable syscall. + */ + if (h->thread_info_flags & _TIF_RESTARTBLOCK) { + set_thread_flag(TIF_RESTART_SVC); + set_thread_flag(TIF_RESTARTBLOCK); + } + + /* need to do something with TIF_RESTORE_SIGMASK ? */ + + ckpt_hdr_put(ctx, h); return 0; } diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S index 9aff1d4..798ea9c 100644 --- a/arch/s390/kernel/entry64.S +++ b/arch/s390/kernel/entry64.S @@ -58,6 +58,7 @@ _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \ _TIF_MCCK_PENDING) _TIF_SYSCALL = (_TIF_SYSCALL_TRACE>>8 | _TIF_SYSCALL_AUDIT>>8 | \ _TIF_SECCOMP>>8 | _TIF_SYSCALL_TRACEPOINT>>8) +CLR_TIF_RESTARTBLOCK = (255 - (_TIF_RESTARTBLOCK>>16)) #define BASED(name) name-system_call(%r13) @@ -338,6 +339,7 @@ sysc_mcck_pending: # sysc_sigpending: ni __TI_flags+7(%r9),255-_TIF_SINGLE_STEP # clear TIF_SINGLE_STEP + ni __TI_flags+6(%r9),CLR_TIF_RESTARTBLOCK # clear TIF_RESTARTBLOCK la %r2,SP_PTREGS(%r15) # load pt_regs brasl %r14,do_signal # call do_signal tm __TI_flags+7(%r9),_TIF_RESTART_SVC diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c index 6b4fef8..503fd09 100644 --- a/arch/s390/kernel/signal.c +++ b/arch/s390/kernel/signal.c @@ -458,6 +458,8 @@ void do_signal(struct pt_regs *regs) regs->psw.addr = restart_addr; break; case -ERESTART_RESTARTBLOCK: + /* if checkpointed here, set needs_restart */ + set_thread_flag(TIF_RESTARTBLOCK); regs->gprs[2] = -EINTR; } regs->svcnr = 0; /* Don't deal with this again. */ @@ -467,6 +469,10 @@ void do_signal(struct pt_regs *regs) the debugger may change all our registers ... */ signr = get_signal_to_deliver(&info, &ka, regs, NULL); + /* we've passed the try_to_freeze() in get_signal_to_deliver(), won't + * be checkpointed before end of do_signal() */ + 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) { -- 1.6.1 -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
