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Subject[PATCH 10/11] uml: avoid malloc to sleep in atomic sections
Date
From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

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 <blaisorblade@yahoo.it>
---

arch/um/include/kern_util.h | 4 +++-
arch/um/include/user.h | 1 +
arch/um/kernel/helper.c | 4 ++--
arch/um/kernel/main.c | 11 +++++++----
arch/um/kernel/process_kern.c | 21 +++++++++++++--------
5 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/arch/um/include/kern_util.h b/arch/um/include/kern_util.h
--- a/arch/um/include/kern_util.h
+++ b/arch/um/include/kern_util.h
@@ -109,9 +109,11 @@ 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);
+
#endif

/*
diff --git a/arch/um/include/user.h b/arch/um/include/user.h
--- 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/helper.c b/arch/um/kernel/helper.c
--- a/arch/um/kernel/helper.c
+++ b/arch/um/kernel/helper.c
@@ -61,7 +61,7 @@ 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 *);
diff --git a/arch/um/kernel/main.c b/arch/um/kernel/main.c
--- a/arch/um/kernel/main.c
+++ b/arch/um/kernel/main.c
@@ -197,11 +197,14 @@ void *__wrap_malloc(int size)
{
void *ret;

- if(!CAN_KMALLOC())
+ if (!CAN_KMALLOC())
return(__real_malloc(size));
- else if(size <= PAGE_SIZE) /* finding contiguos pages can be hard*/
- ret = um_kmalloc(size);
- else ret = um_vmalloc(size);
+ else if (size <= PAGE_SIZE) /* finding contiguos pages can be hard*/
+ ret = __cant_sleep() ? um_kmalloc_atomic(size) :
+ um_kmalloc(size);
+ else
+ ret = __cant_sleep() ? um_vmalloc_atomic(size) :
+ um_vmalloc(size);

/* glibc people insist that if malloc fails, errno should be
* set by malloc as well. So we do.
diff --git a/arch/um/kernel/process_kern.c b/arch/um/kernel/process_kern.c
--- a/arch/um/kernel/process_kern.c
+++ b/arch/um/kernel/process_kern.c
@@ -287,17 +287,27 @@ 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)
@@ -373,11 +383,6 @@ int smp_sigio_handler(void)
return(0);
}

-int um_in_interrupt(void)
-{
- return(in_interrupt());
-}
-
int cpu(void)
{
return(current_thread->cpu);
-
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