From: Paolo 'Blaisorblade' Giarrusso <[email protected]>
Ugly trick to help make malloc not sleeping - we can't do anything else. But
this is not yet optimal, since spinlock don't trigger in_atomic() when
preemption is disabled.
Also, even if ugly, this was already used in one place, and was even more bogus.
Fix it.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[email protected]>
---
arch/um/include/kern_util.h | 4 +++-
arch/um/include/user.h | 1 +
arch/um/kernel/process_kern.c | 21 +++++++++++++--------
arch/um/os-Linux/helper.c | 4 ++--
4 files changed, 19 insertions(+), 11 deletions(-)
diff --git a/arch/um/include/kern_util.h b/arch/um/include/kern_util.h
index 8f4e46d..c649108 100644
--- a/arch/um/include/kern_util.h
+++ b/arch/um/include/kern_util.h
@@ -120,8 +120,10 @@ extern void machine_halt(void);
extern int is_syscall(unsigned long addr);
extern void arch_switch(void);
extern void free_irq(unsigned int, void *);
-extern int um_in_interrupt(void);
extern int cpu(void);
+
+/* Are we disallowed to sleep? Used to choose between GFP_KERNEL and GFP_ATOMIC. */
+extern int __cant_sleep(void);
extern void segv_handler(int sig, union uml_pt_regs *regs);
extern void sigio_handler(int sig, union uml_pt_regs *regs);
diff --git a/arch/um/include/user.h b/arch/um/include/user.h
index 0f865ef..91b0ac4 100644
--- a/arch/um/include/user.h
+++ b/arch/um/include/user.h
@@ -18,6 +18,7 @@ extern int open_gdb_chan(void);
extern unsigned long strlcpy(char *, const char *, unsigned long);
extern unsigned long strlcat(char *, const char *, unsigned long);
extern void *um_vmalloc(int size);
+extern void *um_vmalloc_atomic(int size);
extern void vfree(void *ptr);
#endif
diff --git a/arch/um/kernel/process_kern.c b/arch/um/kernel/process_kern.c
index 7f13b85..d852c55 100644
--- a/arch/um/kernel/process_kern.c
+++ b/arch/um/kernel/process_kern.c
@@ -288,17 +288,27 @@ EXPORT_SYMBOL(disable_hlt);
void *um_kmalloc(int size)
{
- return(kmalloc(size, GFP_KERNEL));
+ return kmalloc(size, GFP_KERNEL);
}
void *um_kmalloc_atomic(int size)
{
- return(kmalloc(size, GFP_ATOMIC));
+ return kmalloc(size, GFP_ATOMIC);
}
void *um_vmalloc(int size)
{
- return(vmalloc(size));
+ return vmalloc(size);
+}
+
+void *um_vmalloc_atomic(int size)
+{
+ return __vmalloc(size, GFP_ATOMIC | __GFP_HIGHMEM, PAGE_KERNEL);
+}
+
+int __cant_sleep(void) {
+ return in_atomic() || irqs_disabled() || in_interrupt();
+ /* Is in_interrupt() really needed? */
}
unsigned long get_fault_addr(void)
@@ -370,11 +380,6 @@ int smp_sigio_handler(void)
return(0);
}
-int um_in_interrupt(void)
-{
- return(in_interrupt());
-}
-
int cpu(void)
{
return(current_thread->cpu);
diff --git a/arch/um/os-Linux/helper.c b/arch/um/os-Linux/helper.c
index 36cc847..6490a4f 100644
--- a/arch/um/os-Linux/helper.c
+++ b/arch/um/os-Linux/helper.c
@@ -60,7 +60,7 @@ int run_helper(void (*pre_exec)(void *),
if((stack_out != NULL) && (*stack_out != 0))
stack = *stack_out;
- else stack = alloc_stack(0, um_in_interrupt());
+ else stack = alloc_stack(0, __cant_sleep());
if(stack == 0)
return(-ENOMEM);
@@ -124,7 +124,7 @@ int run_helper_thread(int (*proc)(void *
unsigned long stack, sp;
int pid, status, err;
- stack = alloc_stack(stack_order, um_in_interrupt());
+ stack = alloc_stack(stack_order, __cant_sleep());
if(stack == 0) return(-ENOMEM);
sp = stack + (page_size() << stack_order) - sizeof(void *);
"Paolo 'Blaisorblade' Giarrusso" <[email protected]> wrote:
>
> +int __cant_sleep(void) {
> + return in_atomic() || irqs_disabled() || in_interrupt();
aww, man, this is awful. Code is supposed to know what context it's
running in, not go fishing about in core internals trying to fix up its own
confusion.
> + /* Is in_interrupt() really needed? */
> }
Yes, it is. in_atomic() is a no-op on !PREEMPT and local irq's can be
enabled in soft- or hard- interrupt context, so irqs_disabled() will return
0.
On Wednesday 18 January 2006 01:56, Andrew Morton wrote:
> "Paolo 'Blaisorblade' Giarrusso" <[email protected]> wrote:
> > +int __cant_sleep(void) {
> > + return in_atomic() || irqs_disabled() || in_interrupt();
>
> aww, man, this is awful. Code is supposed to know what context it's
> running in, not go fishing about in core internals trying to fix up its own
> confusion.
Yes, I know.
But is libc supposed too? That's our problem. This code is only used for calls
to malloc() (not kmalloc()) after the kernel has booted.
There are a few calls to malloc in our code, ok, and those should be fixed
too.
But the main problem are glibc ones (which are called from all kinds of places
- we once got a crash because opendir() was calling malloc with big sizes -
we solved that by optionally using vmalloc()).
--
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade
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