On Thu, Aug 25, 2011 at 7:55 AM, Russell King - ARM Linux
<[email protected]> wrote:
> On Thu, Aug 25, 2011 at 03:09:07PM +0200, Tejun Heo wrote:
>> Hey, Russell.
>>
>> If you can fix it properly without going through temporary step,
>> that's awesome. ?Let's put the arguments behind, okay?
>
> Here's the patch. ?As the kernel I've run this against doesn't have the
> change to try_to_freeze(), I added a might_sleep() in do_signal() during
> my testing to verify that it fixes Mark's problem (which it does.)
>
> I've tested functions returning -ERESTARTSYS, -ERESTARTNOHAND and
> -ERESTART_RESTARTBLOCK, all of which seem to behave as expected with
> signals such as SIGCONT (without handler) and SIGALRM (with handler).
> I haven't tested -ERESTARTNOINTR.
>
> I don't have a test case for the race condition I mentioned (which is
> admittedly pretty difficult to construct, requiring an explicit
> signal, schedule, signal sequence) but this should plug that too.
>
> How do we achieve this? ?Effectively the steps in this patch are:
>
> 1. Undo Arnd's fixups to the syscall restart processing (but don't worry,
> ? we restore it in step 3).
>
> 2. Introduce TIF_SYS_RESTART, which is set when we enter signal handling
> ? and the syscall has returned one of the restart codes. ?This is used
> ? as a flag to indicate that we have some syscall restart processing to
> ? do at some point.
>
> 3. Clear TIF_SYS_RESTART whenever ptrace is used to set the GP registers
> ? (thereby restoring Arnd's fixup for his gdb testsuite problem - it
> ? would be good if Arnd could reconfirm that.)
>
> 4. When we setup a user handler to run, check TIF_SYS_RESTART and clear it.
> ? If it was set, we need to set things up to return -EINTR or restart the
> ? syscall as appropriate. ?As we've cleared it, no further restart
> ? processing will occur.
>
> 5. Once we've run all work (signal delivery, and rescheduling events), and
> ? we're about to return to userspace, make a final check for TIF_SYS_RESTART.
> ? If it's still set, then we're returning to userspace having not setup
> ? any user handlers, and we need to restart the syscall. ?This is mostly
> ? trivial, except for OABI restartblock which requires the user stack to
> ? be written. ?We have to re-enable IRQs for this write, which means we
> ? have to manually re-check for rescheduling events, abort the restart,
> ? and try again later.
>
> One of the side effects of reverting Arnd's patch is that we restore the
> strace behaviour which we've had for years on ARM, and can still be seen
> on x86: strace can see the -ERESTART return codes from the kernel syscalls,
> rather than what seems to be the signal number:
>
> Before:
> rt_sigsuspend([] <unfinished ...>
> --- SIGIO (I/O possible) ---
> <... rt_sigsuspend resumed> ) ? ? ? ? ? = 29
> sigreturn() ? ? ? ? ? ? ? ? ? ? ? ? ? ? = ? (mask now [])
>
> vs:
> rt_sigsuspend([]) ? ? ? ? ? ? ? ? ? ? ? = ? ERESTARTNOHAND (To be restarted)
> --- SIGIO (I/O possible) @ 0 (0) ---
> sigreturn() ? ? ? ? ? ? ? ? ? ? ? ? ? ? = ? (mask now [])
>
> x86:
> rt_sigsuspend([]) ? ? ? ? ? ? ? ? ? ? ? = ? ERESTARTNOHAND (To be restarted)
> --- {si_signo=SIGIO, si_code=SI_USER} (I/O possible) ---
> sigreturn() ? ? ? ? ? ? ? ? ? ? ? ? ? ? = ? (mask now [])
>
> So, this patch should fix:
> 1. The race which I identified in the signal handling code (I think x86
> ? and other architectures can suffer from it too.)
> 2. The warning from try_to_freeze.
> 3. The unanticipated change to strace output.
>
> Arnd, can you test this to make sure your gdb test case still works, and
> Mark, can you test this to make sure it fixes your problem please?
>
> Thanks.
>
Hi Russell,
We are seeing this on ARM with a 3.4 kernel. How was it eventually
resolved? This patch isn't in any tree and I can't find any patch in
linus/master or in any ARM tree that looks like it fixes this.
Here is a trace:
[ 968.040000] BUG: sleeping function called from invalid context at
include/linux/freezer.h:46
[ 968.050000] in_atomic(): 0, irqs_disabled(): 128, pid: 1, name: init
[ 968.060000] [<8001550c>] (unwind_backtrace+0x0/0xec) from
[<805050c4>] (dump_stack+0x20/0x24)
[ 968.060000] [<805050c4>] (dump_stack+0x20/0x24) from [<80052db8>]
(__might_sleep+0xec/0x10c)
[ 968.070000] [<80052db8>] (__might_sleep+0xec/0x10c) from
[<80011290>] (do_signal+0x94/0x54c)
[ 968.080000] [<80011290>] (do_signal+0x94/0x54c) from [<80011c24>]
(do_notify_resume+0x28/0x60)
[ 968.090000] [<80011c24>] (do_notify_resume+0x28/0x60) from
[<8000e018>] (work_pending+0x24/0x28)
Regards,
Mandeep
> ?arch/arm/include/asm/thread_info.h | ? ?3 +
> ?arch/arm/kernel/entry-common.S ? ? | ? 11 ++
> ?arch/arm/kernel/ptrace.c ? ? ? ? ? | ? ?2 +
> ?arch/arm/kernel/signal.c ? ? ? ? ? | ?209 ++++++++++++++++++++++++------------
> ?4 files changed, 155 insertions(+), 70 deletions(-)
>
> diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
> index 7b5cc8d..40df533 100644
> --- a/arch/arm/include/asm/thread_info.h
> +++ b/arch/arm/include/asm/thread_info.h
> @@ -129,6 +129,7 @@ extern void vfp_flush_hwstate(struct thread_info *);
> ?/*
> ?* thread information flags:
> ?* ?TIF_SYSCALL_TRACE ?- syscall trace active
> + * ?TIF_SYS_RESTART ? ?- syscall restart processing
> ?* ?TIF_SIGPENDING ? ? - signal pending
> ?* ?TIF_NEED_RESCHED ? - rescheduling necessary
> ?* ?TIF_NOTIFY_RESUME ?- callback before returning to user
> @@ -139,6 +140,7 @@ extern void vfp_flush_hwstate(struct thread_info *);
> ?#define TIF_NEED_RESCHED ? ? ? 1
> ?#define TIF_NOTIFY_RESUME ? ? ?2 ? ? ? /* callback before returning to user */
> ?#define TIF_SYSCALL_TRACE ? ? ?8
> +#define TIF_SYS_RESTART ? ? ? ? ? ? ? ?9
> ?#define TIF_POLLING_NRFLAG ? ? 16
> ?#define TIF_USING_IWMMXT ? ? ? 17
> ?#define TIF_MEMDIE ? ? ? ? ? ? 18 ? ? ?/* is terminating due to OOM killer */
> @@ -147,6 +149,7 @@ extern void vfp_flush_hwstate(struct thread_info *);
> ?#define TIF_SECCOMP ? ? ? ? ? ?21
>
> ?#define _TIF_SIGPENDING ? ? ? ? ? ? ? ?(1 << TIF_SIGPENDING)
> +#define _TIF_SYS_RESTART ? ? ? (1 << TIF_SYS_RESTART)
> ?#define _TIF_NEED_RESCHED ? ? ?(1 << TIF_NEED_RESCHED)
> ?#define _TIF_NOTIFY_RESUME ? ? (1 << TIF_NOTIFY_RESUME)
> ?#define _TIF_SYSCALL_TRACE ? ? (1 << TIF_SYSCALL_TRACE)
> diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
> index b2a27b6..e922b85 100644
> --- a/arch/arm/kernel/entry-common.S
> +++ b/arch/arm/kernel/entry-common.S
> @@ -45,6 +45,7 @@ ret_fast_syscall:
> ?fast_work_pending:
> ? ? ? ?str ? ? r0, [sp, #S_R0+S_OFF]! ? ? ? ? ?@ returned r0
> ?work_pending:
> + ? ? ? enable_irq
> ? ? ? ?tst ? ? r1, #_TIF_NEED_RESCHED
> ? ? ? ?bne ? ? work_resched
> ? ? ? ?tst ? ? r1, #_TIF_SIGPENDING|_TIF_NOTIFY_RESUME
> @@ -56,6 +57,13 @@ work_pending:
> ? ? ? ?bl ? ? ?do_notify_resume
> ? ? ? ?b ? ? ? ret_slow_syscall ? ? ? ? ? ? ? ?@ Check work again
>
> +work_syscall_restart:
> + ? ? ? mov ? ? r0, sp ? ? ? ? ? ? ? ? ? ? ? ? ?@ 'regs'
> + ? ? ? bl ? ? ?syscall_restart ? ? ? ? ? ? ? ? @ process system call restart
> + ? ? ? teq ? ? r0, #0 ? ? ? ? ? ? ? ? ? ? ? ? ?@ if ret=0 -> success, so
> + ? ? ? beq ? ? ret_restart ? ? ? ? ? ? ? ? ? ? @ return to userspace directly
> + ? ? ? b ? ? ? ret_slow_syscall ? ? ? ? ? ? ? ?@ otherwise, we have a segfault
> +
> ?work_resched:
> ? ? ? ?bl ? ? ?schedule
> ?/*
> @@ -69,6 +77,9 @@ ENTRY(ret_to_user_from_irq)
> ? ? ? ?tst ? ? r1, #_TIF_WORK_MASK
> ? ? ? ?bne ? ? work_pending
> ?no_work_pending:
> + ? ? ? tst ? ? r1, #_TIF_SYS_RESTART
> + ? ? ? bne ? ? work_syscall_restart
> +ret_restart:
> ?#if defined(CONFIG_IRQSOFF_TRACER)
> ? ? ? ?asm_trace_hardirqs_on
> ?#endif
> diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
> index 2491f3b..ac8c34e 100644
> --- a/arch/arm/kernel/ptrace.c
> +++ b/arch/arm/kernel/ptrace.c
> @@ -177,6 +177,7 @@ put_user_reg(struct task_struct *task, int offset, long data)
>
> ? ? ? ?if (valid_user_regs(&newregs)) {
> ? ? ? ? ? ? ? ?regs->uregs[offset] = data;
> + ? ? ? ? ? ? ? clear_ti_thread_flag(task_thread_info(task), TIF_SYS_RESTART);
> ? ? ? ? ? ? ? ?ret = 0;
> ? ? ? ?}
>
> @@ -604,6 +605,7 @@ static int gpr_set(struct task_struct *target,
> ? ? ? ? ? ? ? ?return -EINVAL;
>
> ? ? ? ?*task_pt_regs(target) = newregs;
> + ? ? ? clear_ti_thread_flag(task_thread_info(target), TIF_SYS_RESTART);
> ? ? ? ?return 0;
> ?}
>
> diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
> index 0340224..42a1521 100644
> --- a/arch/arm/kernel/signal.c
> +++ b/arch/arm/kernel/signal.c
> @@ -649,6 +649,135 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
> ?}
>
> ?/*
> + * Syscall restarting codes
> + *
> + * -ERESTARTSYS: restart system call if no handler, or if there is a
> + * ? ? handler but it's marked SA_RESTART. ?Otherwise return -EINTR.
> + * -ERESTARTNOINTR: always restart system call
> + * -ERESTARTNOHAND: restart system call only if no handler, otherwise
> + * ? ? return -EINTR if invoking a user signal handler.
> + * -ERESTART_RESTARTBLOCK: call restart syscall if no handler, otherwise
> + * ? ? return -EINTR if invoking a user signal handler.
> + */
> +static void setup_syscall_restart(struct pt_regs *regs)
> +{
> + ? ? ? regs->ARM_r0 = regs->ARM_ORIG_r0;
> + ? ? ? regs->ARM_pc -= thumb_mode(regs) ? 2 : 4;
> +}
> +
> +/*
> + * Depending on the signal settings we may need to revert the decision
> + * to restart the system call. ?But skip this if a debugger has chosen
> + * to restart at a different PC.
> + */
> +static void syscall_restart_handler(struct pt_regs *regs, struct k_sigaction *ka)
> +{
> + ? ? ? if (test_and_clear_thread_flag(TIF_SYS_RESTART)) {
> + ? ? ? ? ? ? ? long r0 = regs->ARM_r0;
> +
> + ? ? ? ? ? ? ? /*
> + ? ? ? ? ? ? ? ?* By default, return -EINTR to the user process for any
> + ? ? ? ? ? ? ? ?* syscall which would otherwise be restarted.
> + ? ? ? ? ? ? ? ?*/
> + ? ? ? ? ? ? ? regs->ARM_r0 = -EINTR;
> +
> + ? ? ? ? ? ? ? if (r0 == -ERESTARTNOINTR ||
> + ? ? ? ? ? ? ? ? ? (r0 == -ERESTARTSYS && !(ka->sa.sa_flags & SA_RESTART)))
> + ? ? ? ? ? ? ? ? ? ? ? setup_syscall_restart(regs);
> + ? ? ? }
> +}
> +
> +/*
> + * Handle syscall restarting when there is no user handler in place for
> + * a delivered signal. ?Rather than doing this as part of the normal
> + * signal processing, we do this on the final return to userspace, after
> + * we've finished handling signals and checking for schedule events.
> + *
> + * This avoids bad behaviour such as:
> + * ?- syscall returns -ERESTARTNOHAND
> + * ?- signal with no handler (so we set things up to restart the syscall)
> + * ?- schedule
> + * ?- signal with handler (eg, SIGALRM)
> + * ?- we call the handler and then restart the syscall
> + *
> + * In order to avoid races with TIF_NEED_RESCHED, IRQs must be disabled
> + * when this function is called and remain disabled until we exit to
> + * userspace.
> + */
> +asmlinkage int syscall_restart(struct pt_regs *regs)
> +{
> + ? ? ? struct thread_info *thread = current_thread_info();
> +
> + ? ? ? clear_ti_thread_flag(thread, TIF_SYS_RESTART);
> +
> + ? ? ? /*
> + ? ? ? ?* Restart the system call. ?We haven't setup a signal handler
> + ? ? ? ?* to invoke, and the regset hasn't been usurped by ptrace.
> + ? ? ? ?*/
> + ? ? ? if (regs->ARM_r0 == -ERESTART_RESTARTBLOCK) {
> + ? ? ? ? ? ? ? if (thumb_mode(regs)) {
> + ? ? ? ? ? ? ? ? ? ? ? regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE;
> + ? ? ? ? ? ? ? ? ? ? ? regs->ARM_pc -= 2;
> + ? ? ? ? ? ? ? } else {
> +#if defined(CONFIG_AEABI) && !defined(CONFIG_OABI_COMPAT)
> + ? ? ? ? ? ? ? ? ? ? ? regs->ARM_r7 = __NR_restart_syscall;
> + ? ? ? ? ? ? ? ? ? ? ? regs->ARM_pc -= 4;
> +#else
> + ? ? ? ? ? ? ? ? ? ? ? u32 sp = regs->ARM_sp - 4;
> + ? ? ? ? ? ? ? ? ? ? ? u32 __user *usp = (u32 __user *)sp;
> + ? ? ? ? ? ? ? ? ? ? ? int ret;
> +
> + ? ? ? ? ? ? ? ? ? ? ? /*
> + ? ? ? ? ? ? ? ? ? ? ? ?* For OABI, we need to play some extra games, because
> + ? ? ? ? ? ? ? ? ? ? ? ?* we need to write to the users stack, which we can't
> + ? ? ? ? ? ? ? ? ? ? ? ?* do reliably from IRQs-disabled context. ?Temporarily
> + ? ? ? ? ? ? ? ? ? ? ? ?* re-enable IRQs, perform the store, and then plug
> + ? ? ? ? ? ? ? ? ? ? ? ?* the resulting race afterwards.
> + ? ? ? ? ? ? ? ? ? ? ? ?*/
> + ? ? ? ? ? ? ? ? ? ? ? local_irq_enable();
> + ? ? ? ? ? ? ? ? ? ? ? ret = put_user(regs->ARM_pc, usp);
> + ? ? ? ? ? ? ? ? ? ? ? local_irq_disable();
> +
> + ? ? ? ? ? ? ? ? ? ? ? /*
> + ? ? ? ? ? ? ? ? ? ? ? ?* Plug the reschedule race - if we need to reschedule,
> + ? ? ? ? ? ? ? ? ? ? ? ?* abort the syscall restarting. ?We haven't modified
> + ? ? ? ? ? ? ? ? ? ? ? ?* anything other than the attempted write to the stack
> + ? ? ? ? ? ? ? ? ? ? ? ?* so we can merely retry later.
> + ? ? ? ? ? ? ? ? ? ? ? ?*/
> + ? ? ? ? ? ? ? ? ? ? ? if (need_resched()) {
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? set_ti_thread_flag(thread, TIF_SYS_RESTART);
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? return -EINTR;
> + ? ? ? ? ? ? ? ? ? ? ? }
> +
> + ? ? ? ? ? ? ? ? ? ? ? /*
> + ? ? ? ? ? ? ? ? ? ? ? ?* We failed (for some reason) to write to the stack.
> + ? ? ? ? ? ? ? ? ? ? ? ?* Terminate the task.
> + ? ? ? ? ? ? ? ? ? ? ? ?*/
> + ? ? ? ? ? ? ? ? ? ? ? if (ret) {
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? force_sigsegv(0, current);
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? return -EFAULT;
> + ? ? ? ? ? ? ? ? ? ? ? }
> +
> + ? ? ? ? ? ? ? ? ? ? ? /*
> + ? ? ? ? ? ? ? ? ? ? ? ?* Success, update the stack pointer and point the
> + ? ? ? ? ? ? ? ? ? ? ? ?* PC at the restarting code.
> + ? ? ? ? ? ? ? ? ? ? ? ?*/
> + ? ? ? ? ? ? ? ? ? ? ? regs->ARM_sp = sp;
> + ? ? ? ? ? ? ? ? ? ? ? regs->ARM_pc = KERN_RESTART_CODE;
> +#endif
> + ? ? ? ? ? ? ? }
> + ? ? ? } else {
> + ? ? ? ? ? ? ? /*
> + ? ? ? ? ? ? ? ?* Simple restart - just back up and re-execute the last
> + ? ? ? ? ? ? ? ?* instruction.
> + ? ? ? ? ? ? ? ?*/
> + ? ? ? ? ? ? ? setup_syscall_restart(regs);
> + ? ? ? }
> +
> + ? ? ? return 0;
> +}
> +
> +/*
> ?* Note that 'init' is a special process: it doesn't get signals it doesn't
> ?* want to handle. Thus you cannot kill init even with a SIGKILL even by
> ?* mistake.
> @@ -659,7 +788,6 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
> ?*/
> ?static void do_signal(struct pt_regs *regs, int syscall)
> ?{
> - ? ? ? unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
> ? ? ? ?struct k_sigaction ka;
> ? ? ? ?siginfo_t info;
> ? ? ? ?int signr;
> @@ -674,32 +802,16 @@ static void do_signal(struct pt_regs *regs, int syscall)
> ? ? ? ? ? ? ? ?return;
>
> ? ? ? ?/*
> - ? ? ? ?* If we were from a system call, check for system call restarting...
> + ? ? ? ?* Set the SYS_RESTART flag to indicate that we have some
> + ? ? ? ?* cleanup of the restart state to perform when returning to
> + ? ? ? ?* userspace.
> ? ? ? ? */
> - ? ? ? if (syscall) {
> - ? ? ? ? ? ? ? continue_addr = regs->ARM_pc;
> - ? ? ? ? ? ? ? restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
> - ? ? ? ? ? ? ? retval = regs->ARM_r0;
> -
> - ? ? ? ? ? ? ? /*
> - ? ? ? ? ? ? ? ?* Prepare for system call restart. ?We do this here so that a
> - ? ? ? ? ? ? ? ?* debugger will see the already changed PSW.
> - ? ? ? ? ? ? ? ?*/
> - ? ? ? ? ? ? ? switch (retval) {
> - ? ? ? ? ? ? ? case -ERESTARTNOHAND:
> - ? ? ? ? ? ? ? case -ERESTARTSYS:
> - ? ? ? ? ? ? ? case -ERESTARTNOINTR:
> - ? ? ? ? ? ? ? ? ? ? ? regs->ARM_r0 = regs->ARM_ORIG_r0;
> - ? ? ? ? ? ? ? ? ? ? ? regs->ARM_pc = restart_addr;
> - ? ? ? ? ? ? ? ? ? ? ? break;
> - ? ? ? ? ? ? ? case -ERESTART_RESTARTBLOCK:
> - ? ? ? ? ? ? ? ? ? ? ? regs->ARM_r0 = -EINTR;
> - ? ? ? ? ? ? ? ? ? ? ? break;
> - ? ? ? ? ? ? ? }
> - ? ? ? }
> -
> - ? ? ? if (try_to_freeze())
> - ? ? ? ? ? ? ? goto no_signal;
> + ? ? ? if (syscall &&
> + ? ? ? ? ? (regs->ARM_r0 == -ERESTARTSYS ||
> + ? ? ? ? ? ?regs->ARM_r0 == -ERESTARTNOINTR ||
> + ? ? ? ? ? ?regs->ARM_r0 == -ERESTARTNOHAND ||
> + ? ? ? ? ? ?regs->ARM_r0 == -ERESTART_RESTARTBLOCK))
> + ? ? ? ? ? ? ? set_thread_flag(TIF_SYS_RESTART);
>
> ? ? ? ?/*
> ? ? ? ? * Get the signal to deliver. ?When running under ptrace, at this
> @@ -709,19 +821,7 @@ static void do_signal(struct pt_regs *regs, int syscall)
> ? ? ? ?if (signr > 0) {
> ? ? ? ? ? ? ? ?sigset_t *oldset;
>
> - ? ? ? ? ? ? ? /*
> - ? ? ? ? ? ? ? ?* Depending on the signal settings we may need to revert the
> - ? ? ? ? ? ? ? ?* decision to restart the system call. ?But skip this if a
> - ? ? ? ? ? ? ? ?* debugger has chosen to restart at a different PC.
> - ? ? ? ? ? ? ? ?*/
> - ? ? ? ? ? ? ? if (regs->ARM_pc == restart_addr) {
> - ? ? ? ? ? ? ? ? ? ? ? if (retval == -ERESTARTNOHAND
> - ? ? ? ? ? ? ? ? ? ? ? ? ? || (retval == -ERESTARTSYS
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? && !(ka.sa.sa_flags & SA_RESTART))) {
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? regs->ARM_r0 = -EINTR;
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? regs->ARM_pc = continue_addr;
> - ? ? ? ? ? ? ? ? ? ? ? }
> - ? ? ? ? ? ? ? }
> + ? ? ? ? ? ? ? syscall_restart_handler(regs, &ka);
>
> ? ? ? ? ? ? ? ?if (test_thread_flag(TIF_RESTORE_SIGMASK))
> ? ? ? ? ? ? ? ? ? ? ? ?oldset = ¤t->saved_sigmask;
> @@ -740,38 +840,7 @@ static void do_signal(struct pt_regs *regs, int syscall)
> ? ? ? ? ? ? ? ?return;
> ? ? ? ?}
>
> - no_signal:
> ? ? ? ?if (syscall) {
> - ? ? ? ? ? ? ? /*
> - ? ? ? ? ? ? ? ?* Handle restarting a different system call. ?As above,
> - ? ? ? ? ? ? ? ?* if a debugger has chosen to restart at a different PC,
> - ? ? ? ? ? ? ? ?* ignore the restart.
> - ? ? ? ? ? ? ? ?*/
> - ? ? ? ? ? ? ? if (retval == -ERESTART_RESTARTBLOCK
> - ? ? ? ? ? ? ? ? ? && regs->ARM_pc == continue_addr) {
> - ? ? ? ? ? ? ? ? ? ? ? if (thumb_mode(regs)) {
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE;
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? regs->ARM_pc -= 2;
> - ? ? ? ? ? ? ? ? ? ? ? } else {
> -#if defined(CONFIG_AEABI) && !defined(CONFIG_OABI_COMPAT)
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? regs->ARM_r7 = __NR_restart_syscall;
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? regs->ARM_pc -= 4;
> -#else
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? u32 __user *usp;
> -
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? regs->ARM_sp -= 4;
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? usp = (u32 __user *)regs->ARM_sp;
> -
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? if (put_user(regs->ARM_pc, usp) == 0) {
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? regs->ARM_pc = KERN_RESTART_CODE;
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? } else {
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? regs->ARM_sp += 4;
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? force_sigsegv(0, current);
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? }
> -#endif
> - ? ? ? ? ? ? ? ? ? ? ? }
> - ? ? ? ? ? ? ? }
> -
> ? ? ? ? ? ? ? ?/* If there's no signal to deliver, we just put the saved sigmask
> ? ? ? ? ? ? ? ? * back.
> ? ? ? ? ? ? ? ? */
>
> --
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On Tue, Jun 26, 2012 at 09:39:14AM -0700, Mandeep Singh Baines wrote:
> Hi Russell,
>
> We are seeing this on ARM with a 3.4 kernel. How was it eventually
> resolved? This patch isn't in any tree and I can't find any patch in
> linus/master or in any ARM tree that looks like it fixes this.
It's still work in progress.