From: Keith Owens <kaos@sgi.com>
Almost every architecture has a comment above smp_call_function()
* You must not call this function with disabled interrupts or from a
* hardware interrupt handler or from a bottom half handler.
I have not seen any problems with calling smp_call_function() from a bottom
half handler, but calling it with interrupts disabled can definitely
deadlock. This bug is hard to reproduce and even harder to debug.
CPU A CPU B
Disable interrupts
smp_call_function()
Take call_lock
Send IPIs
Wait for all cpus to acknowledge IPI
CPU A has not responded, spin waiting
for cpu A to respond, holding call_lock
smp_call_function()
Spin waiting for call_lock
Deadlock Deadlock
Change all smp_call_function() to WARN_ON(irqs_disabled()). It should be
BUG_ON() but some buggy code like SCSI sg will break with BUG_ON, so just
warn for now. Change it to BUG_ON after the buggy code has been fixed.
---
25-akpm/arch/alpha/kernel/smp.c | 3 +++
25-akpm/arch/i386/kernel/smp.c | 3 +++
25-akpm/arch/i386/mach-voyager/voyager_smp.c | 3 +++
25-akpm/arch/ia64/kernel/smp.c | 3 +++
25-akpm/arch/mips/kernel/smp.c | 3 +++
25-akpm/arch/parisc/kernel/smp.c | 3 +++
25-akpm/arch/ppc/kernel/smp.c | 2 ++
25-akpm/arch/ppc64/kernel/smp.c | 3 +++
25-akpm/arch/s390/kernel/smp.c | 3 +++
25-akpm/arch/sh/kernel/smp.c | 3 +++
25-akpm/arch/sparc64/kernel/smp.c | 3 +++
25-akpm/arch/um/kernel/smp.c | 3 +++
25-akpm/arch/x86_64/kernel/smp.c | 3 +++
13 files changed, 38 insertions(+)
diff -puN arch/alpha/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/alpha/kernel/smp.c
--- 25/arch/alpha/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.823843424 -0700
+++ 25-akpm/arch/alpha/kernel/smp.c 2004-05-04 22:59:50.843840384 -0700
@@ -820,6 +820,9 @@ smp_call_function_on_cpu (void (*func) (
unsigned long timeout;
int num_cpus_to_call;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
data.func = func;
data.info = info;
data.wait = wait;
diff -puN arch/i386/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/i386/kernel/smp.c
--- 25/arch/i386/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.824843272 -0700
+++ 25-akpm/arch/i386/kernel/smp.c 2004-05-04 22:59:50.844840232 -0700
@@ -528,6 +528,9 @@ int smp_call_function (void (*func) (voi
if (!cpus)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
data.func = func;
data.info = info;
atomic_set(&data.started, 0);
diff -puN arch/i386/mach-voyager/voyager_smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/i386/mach-voyager/voyager_smp.c
--- 25/arch/i386/mach-voyager/voyager_smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.826842968 -0700
+++ 25-akpm/arch/i386/mach-voyager/voyager_smp.c 2004-05-04 22:59:50.845840080 -0700
@@ -1105,6 +1105,9 @@ smp_call_function (void (*func) (void *i
if (!mask)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
data.func = func;
data.info = info;
data.started = mask;
diff -puN arch/ia64/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/ia64/kernel/smp.c
--- 25/arch/ia64/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.827842816 -0700
+++ 25-akpm/arch/ia64/kernel/smp.c 2004-05-04 22:59:50.846839928 -0700
@@ -308,6 +308,9 @@ smp_call_function (void (*func) (void *i
if (!cpus)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
data.func = func;
data.info = info;
atomic_set(&data.started, 0);
diff -puN arch/mips/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/mips/kernel/smp.c
--- 25/arch/mips/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.829842512 -0700
+++ 25-akpm/arch/mips/kernel/smp.c 2004-05-04 22:59:50.846839928 -0700
@@ -151,6 +151,9 @@ int smp_call_function (void (*func) (voi
if (!cpus)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
data.func = func;
data.info = info;
atomic_set(&data.started, 0);
diff -puN arch/parisc/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/parisc/kernel/smp.c
--- 25/arch/parisc/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.830842360 -0700
+++ 25-akpm/arch/parisc/kernel/smp.c 2004-05-04 22:59:50.847839776 -0700
@@ -327,6 +327,9 @@ smp_call_function (void (*func) (void *i
struct smp_call_struct data;
unsigned long timeout;
static spinlock_t lock = SPIN_LOCK_UNLOCKED;
+
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
data.func = func;
data.info = info;
diff -puN arch/ppc64/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/ppc64/kernel/smp.c
--- 25/arch/ppc64/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.831842208 -0700
+++ 25-akpm/arch/ppc64/kernel/smp.c 2004-05-04 22:59:50.848839624 -0700
@@ -692,6 +692,9 @@ int smp_call_function (void (*func) (voi
int ret = -1, cpus;
unsigned long timeout;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
data.func = func;
data.info = info;
atomic_set(&data.started, 0);
diff -puN arch/ppc/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/ppc/kernel/smp.c
--- 25/arch/ppc/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.832842056 -0700
+++ 25-akpm/arch/ppc/kernel/smp.c 2004-05-04 22:59:50.848839624 -0700
@@ -211,6 +211,8 @@ int smp_call_function(void (*func) (void
bitmask. --RR */
if (num_online_cpus() <= 1)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
return __smp_call_function(func, info, wait, MSG_ALL_BUT_SELF);
}
diff -puN arch/s390/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/s390/kernel/smp.c
--- 25/arch/s390/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.834841752 -0700
+++ 25-akpm/arch/s390/kernel/smp.c 2004-05-04 22:59:50.849839472 -0700
@@ -127,6 +127,9 @@ int smp_call_function (void (*func) (voi
if (cpus <= 0)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
data.func = func;
data.info = info;
atomic_set(&data.started, 0);
diff -puN arch/sh/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/sh/kernel/smp.c
--- 25/arch/sh/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.835841600 -0700
+++ 25-akpm/arch/sh/kernel/smp.c 2004-05-04 22:59:50.849839472 -0700
@@ -181,6 +181,9 @@ int smp_call_function(void (*func)(void
if (nr_cpus < 2)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
spin_lock(&smp_fn_call.lock);
atomic_set(&smp_fn_call.finished, 0);
diff -puN arch/sparc64/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/sparc64/kernel/smp.c
--- 25/arch/sparc64/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.836841448 -0700
+++ 25-akpm/arch/sparc64/kernel/smp.c 2004-05-04 22:59:50.850839320 -0700
@@ -598,6 +598,9 @@ int smp_call_function(void (*func)(void
if (!cpus)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
data.func = func;
data.info = info;
atomic_set(&data.finished, 0);
diff -puN arch/um/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/um/kernel/smp.c
--- 25/arch/um/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.838841144 -0700
+++ 25-akpm/arch/um/kernel/smp.c 2004-05-04 22:59:50.851839168 -0700
@@ -266,6 +266,9 @@ int smp_call_function(void (*_func)(void
if (!cpus)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
spin_lock_bh(&call_lock);
atomic_set(&scf_started, 0);
atomic_set(&scf_finished, 0);
diff -puN arch/x86_64/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled arch/x86_64/kernel/smp.c
--- 25/arch/x86_64/kernel/smp.c~warn-when-smp_call_function-is-called-with-interrupts-disabled 2004-05-04 22:59:50.839840992 -0700
+++ 25-akpm/arch/x86_64/kernel/smp.c 2004-05-04 22:59:50.851839168 -0700
@@ -416,6 +416,9 @@ int smp_call_function (void (*func) (voi
if (!cpus)
return 0;
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(irqs_disabled());
+
data.func = func;
data.info = info;
atomic_set(&data.started, 0);
_