From: Johannes Berg
We should be able to ndelay() from any context, even from an
interrupt context! However, this is broken (not functionally,
but locking-wise) in time-travel because we'll get into the
time-travel code and enable interrupts to handle messages on
other time-travel aware subsystems (only virtio for now).
Luckily, I've already reworked the time-travel aware signal
(interrupt) delivery for suspend/resume to have a time travel
handler, which runs directly in the context of the signal and
not from the Linux interrupt.
In order to fix this time-travel issue then, we need to do a
few things:
1) rework the signal handling code to not block SIGIO (if
time-travel is enabled, just to simplify the other case)
but rather let it bubble through the system, all the way
*past* the IRQ's timetravel_handler, stopping it after
that and before real interrupt delivery if IRQs are not
actually enabled;
2) rework time-travel to not enable interrupts while it's
waiting for a message;
3) rework time-travel to not (just) disable interrupts but
rather block signals at a lower level while it needs them
disabled for communicating with the controller.
Finally, since now we can actually spend even virtual time
in interrupts-disabled sections, the delay warning when we
deliver a time-travel delayed interrupt is no longer valid,
things can (and should) now get delayed.
Signed-off-by: Johannes Berg
---
arch/um/include/shared/irq_user.h | 1 +
arch/um/include/shared/os.h | 3 +++
arch/um/kernel/irq.c | 38 +-
arch/um/kernel/time.c | 35 +---
arch/um/os-Linux/signal.c | 44 ---
5 files changed, 88 insertions(+), 33 deletions(-)
diff --git a/arch/um/include/shared/irq_user.h
b/arch/um/include/shared/irq_user.h
index 07239e801a5b..065829f443ae 100644
--- a/arch/um/include/shared/irq_user.h
+++ b/arch/um/include/shared/irq_user.h
@@ -17,6 +17,7 @@ enum um_irq_type {
struct siginfo;
extern void sigio_handler(int sig, struct siginfo *unused_si, struct
uml_pt_regs *regs);
+void sigio_run_timetravel_handlers(void);
extern void free_irq_by_fd(int fd);
extern void deactivate_fd(int fd, int irqnum);
extern int deactivate_all_fds(void);
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 13d86f94cf0f..afd5fbc1c867 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -243,6 +243,9 @@ extern int set_signals_trace(int enable);
extern int os_is_signal_stack(void);
extern void deliver_alarm(void);
extern void register_pm_wake_signal(void);
+extern void block_signals_hard(void);
+extern void unblock_signals_hard(void);
+extern void mark_sigio_pending(void);
/* util.c */
extern void stack_protections(unsigned long address);
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 82af5191e73d..76448b85292f 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -123,7 +123,8 @@ static bool irq_do_timetravel_handler(struct irq_entry
*entry,
#endif
static void sigio_reg_handler(int idx, struct irq_entry *entry, enum
um_irq_type t,
- struct uml_pt_regs *regs)
+ struct uml_pt_regs *regs,
+ bool timetravel_handlers_only)
{
struct irq_reg *reg = &entry->reg[t];
@@ -136,18 +137,32 @@ static void sigio_reg_handler(int idx, struct irq_entry
*entry, enum um_irq_type
if (irq_do_timetravel_handler(entry, t))
return;
- if (irqs_suspended)
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+ /*
+* We can only get here with signals disabled if we have time-travel
+* support, otherwise we cannot have the hard handlers that may need
+* to run even in interrupts-disabled sections and therefore sigio is
+* blocked as well when interrupts are disabled.
+*/
+ if (!get_signals()) {
+ mark_sigio_pending();
+ return;
+ }
+#endif
+
+ if (timetravel_handlers_only)
return;
irq_io_loop(reg, regs);
}
-void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs
*regs)
+static void _sigio_handler(struct uml_pt_regs *regs,
+ bool timetravel_handlers_only)
{
struct irq_entry *irq_entry;
int n, i;
- if (irqs_suspended && !um_irq_timetravel_handler_used())
+ if (timetravel_handlers_only && !um_irq_timetravel_handler_used())
return;
while (1) {
@@ -172,14 +187,20 @@ void sigio_handler(int sig, struct siginfo *unused_si,
struct uml_pt_regs *regs)
irq_entry = os_epoll_get_data_pointer(i);
for (t = 0; t < NUM_IRQ_TYPES; t++)
- sigio_reg_handler(i, irq_entry, t, regs);
+ sigio_reg_handler(i, irq_entry, t, r
