From 7ee2f6c993a829cc24cce819261bc2b6053348cc Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@penguin.transmeta.com>
Date: Sun, 21 Jul 2002 23:42:32 -0700
Subject: [PATCH] Ingo Molnar's update to remove irqlock (documentation and
fixing a number of drivers)
---
Documentation/cli-sti-removal.txt | 39 +++++++++++++++++++++++--------
Documentation/preempt-locking.txt | 7 ++++++
arch/i386/kernel/apic.c | 4 ++++
arch/i386/kernel/bluesmoke.c | 2 ++
arch/i386/kernel/entry.S | 1 -
arch/i386/kernel/smp.c | 2 +-
drivers/net/8139cp.c | 4 +++-
drivers/net/8139too.c | 4 +++-
drivers/net/plip.c | 6 ++---
drivers/net/tulip/de2104x.c | 2 +-
drivers/scsi/qlogicisp.c | 19 ---------------
include/linux/interrupt.h | 10 ++++++++
include/linux/smp.h | 5 ++--
13 files changed, 66 insertions(+), 39 deletions(-)
diff --git a/Documentation/cli-sti-removal.txt b/Documentation/cli-sti-removal.txt
index 8192ffefc711..13c744dac866 100644
--- a/Documentation/cli-sti-removal.txt
+++ b/Documentation/cli-sti-removal.txt
@@ -2,10 +2,10 @@
#### cli()/sti() removal guide, started by Ingo Molnar <mingo@redhat.com>
-as of 2.5.28, four popular macros have been removed on SMP, and
+as of 2.5.28, five popular macros have been removed on SMP, and
are being phased out on UP:
- cli(), sti(), save_flags(flags), restore_flags(flags)
+ cli(), sti(), save_flags(flags), save_flags_cli(flags), restore_flags(flags)
until now it was possible to protect driver code against interrupt
handlers via a cli(), but from now on other, more lightweight methods
@@ -86,25 +86,44 @@ the above code has a number of advantages:
cli() on the other hand was used by many drivers, and extended
the critical section to the whole IRQ handler function - creating
serious lock contention.
-
+
to make the transition easier, we've still kept the cli(), sti(),
-save_flags() and restore_flags() macros defined on UP systems - but
-their usage will be phased out until the 2.6 kernel is released.
+save_flags(), save_flags_cli() and restore_flags() macros defined
+on UP systems - but their usage will be phased out until 2.6 is
+released.
drivers that want to disable local interrupts (interrupts on the
-current CPU), can use the following four macros:
+current CPU), can use the following five macros:
- __cli(), __sti(), __save_flags(flags), __restore_flags(flags)
+ local_irq_disable(), local_irq_enable(), local_irq_save(flags),
+ local_irq_save_off(flags), local_irq_restore(flags)
but beware, their meaning and semantics are much simpler, far from
-that of cli(), sti(), save_flags(flags) and restore_flags(flags).
+that of the old cli(), sti(), save_flags(flags) and restore_flags(flags)
+SMP meaning:
+
+ local_irq_disable() => turn local IRQs off
+
+ local_irq_enable() => turn local IRQs on
+ local_irq_save(flags) => save the current IRQ state into flags. The
+ state can be on or off. (on some
+ architectures there's even more bits in it.)
+
+ local_irq_save_off(flags) => save the current IRQ state into flags and
+ disable interrupts.
+
+ local_irq_restore(flags) => restore the IRQ state from flags.
+
+(local_irq_save can save both irqs on and irqs off state, and
+local_irq_restore can restore into both irqs on and irqs off state.)
another related change is that synchronize_irq() now takes a parameter:
synchronize_irq(irq). This change too has the purpose of making SMP
-synchronization more lightweight - this way you can wait for your own
-interrupt handler to finish, no need to wait for other IRQ sources.
+to make the transition easier, we've still kept the cli(), sti(),
+save_flags() and restore_flags() macros defined on UP systems - but
+their usage will be phased out until the 2.6 kernel is released.
why were these changes done? The main reason was the architectural burden
diff --git a/Documentation/preempt-locking.txt b/Documentation/preempt-locking.txt
index 580814915c70..08e6035a0e13 100644
--- a/Documentation/preempt-locking.txt
+++ b/Documentation/preempt-locking.txt
@@ -82,6 +82,13 @@ Note that you do not need to explicitly prevent preemption if you are holding
any locks or interrupts are disabled, since preemption is implicitly disabled
in those cases.
+But keep in mind that 'irqs disabled' is a fundamentally unsafe way of
+disabling preemption - any spin_unlock() decreasing the preemption count
+to 0 might trigger a reschedule. A simple printk() might trigger a reschedule.
+So use this implicit preemption-disabling property only if you know that the
+affected codepath does not do any of this. Best policy is to use this only for
+small, atomic code that you wrote and which calls no complex functions.
+
Example:
cpucache_t *cc; /* this is per-CPU */
diff --git a/arch/i386/kernel/apic.c b/arch/i386/kernel/apic.c
index 15ba757d2d6b..801d4f2139b1 100644
--- a/arch/i386/kernel/apic.c
+++ b/arch/i386/kernel/apic.c
@@ -1099,6 +1099,7 @@ asmlinkage void smp_spurious_interrupt(void)
{
unsigned long v;
+ irq_enter();
/*
* Check if this really is a spurious interrupt and ACK it
* if it is a vectored one. Just in case...
@@ -1111,6 +1112,7 @@ asmlinkage void smp_spurious_interrupt(void)
/* see sw-dev-man vol 3, chapter 7.4.13.5 */
printk(KERN_INFO "spurious APIC interrupt on CPU#%d, should never happen.\n",
smp_processor_id());
+ irq_exit();
}
/*
@@ -1121,6 +1123,7 @@ asmlinkage void smp_error_interrupt(void)
{
unsigned long v, v1;
+ irq_enter();
/* First tickle the hardware, only then report what went on. -- REW */
v = apic_read(APIC_ESR);
apic_write(APIC_ESR, 0);
@@ -1140,6 +1143,7 @@ asmlinkage void smp_error_interrupt(void)
*/
printk (KERN_ERR "APIC error on CPU%d: %02lx(%02lx)\n",
smp_processor_id(), v , v1);
+ irq_exit();
}
/*
diff --git a/arch/i386/kernel/bluesmoke.c b/arch/i386/kernel/bluesmoke.c
index 9a1c05eddf55..ee0a5ca7f3ca 100644
--- a/arch/i386/kernel/bluesmoke.c
+++ b/arch/i386/kernel/bluesmoke.c
@@ -74,7 +74,9 @@ static void (*vendor_thermal_interrupt)(struct pt_regs *regs) = unexpected_therm
asmlinkage void smp_thermal_interrupt(struct pt_regs regs)
{
+ irq_enter();
vendor_thermal_interrupt(®s);
+ irq_exit();
}
/* P4/Xeon Thermal regulation detect and init */
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index e5f506df8533..641062bbcbf2 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -186,7 +186,6 @@ ENTRY(ret_from_fork)
# userspace resumption stub bypassing syscall exit tracing
ALIGN
ret_from_intr:
- preempt_stop
ret_from_exception:
movl EFLAGS(%esp), %eax # mix EFLAGS and CS
movb CS(%esp), %al
diff --git a/arch/i386/kernel/smp.c b/arch/i386/kernel/smp.c
index 2098fcf2679a..4387535fc71e 100644
--- a/arch/i386/kernel/smp.c
+++ b/arch/i386/kernel/smp.c
@@ -387,7 +387,7 @@ asmlinkage void smp_invalidate_interrupt (void)
clear_bit(cpu, &flush_cpumask);
out:
- put_cpu();
+ put_cpu_no_resched();
}
static void flush_tlb_others (unsigned long cpumask, struct mm_struct *mm,
diff --git a/drivers/net/8139cp.c b/drivers/net/8139cp.c
index 9b7bfac1c4a3..5fa80ade4429 100644
--- a/drivers/net/8139cp.c
+++ b/drivers/net/8139cp.c
@@ -926,13 +926,15 @@ static struct net_device_stats *cp_get_stats(struct net_device *dev)
static void cp_stop_hw (struct cp_private *cp)
{
+ struct net_device *dev = cp->dev;
+
cpw16(IntrMask, 0);
cpr16(IntrMask);
cpw8(Cmd, 0);
cpw16(CpCmd, 0);
cpr16(CpCmd);
cpw16(IntrStatus, ~(cpr16(IntrStatus)));
- synchronize_irq();
+ synchronize_irq(dev->irq);
udelay(10);
cp->rx_tail = 0;
diff --git a/drivers/net/8139too.c b/drivers/net/8139too.c
index 6eb8e2ff52d4..76a257ea33e0 100644
--- a/drivers/net/8139too.c
+++ b/drivers/net/8139too.c
@@ -2130,7 +2130,9 @@ static int rtl8139_close (struct net_device *dev)
spin_unlock_irqrestore (&tp->lock, flags);
- synchronize_irq ();
+ /* TODO: isn't this code racy? we synchronize the IRQ and then free it, */
+ /* but another IRQ could've happened in between the sync and free */
+ synchronize_irq (dev->irq);
free_irq (dev->irq, dev);
rtl8139_tx_clear (tp);
diff --git a/drivers/net/plip.c b/drivers/net/plip.c
index 864d9b833043..47a9422e672c 100644
--- a/drivers/net/plip.c
+++ b/drivers/net/plip.c
@@ -518,7 +518,7 @@ plip_bh_timeout_error(struct net_device *dev, struct net_local *nl,
spin_unlock_irq(&nl->lock);
if (error == HS_TIMEOUT) {
DISABLE(dev->irq);
- synchronize_irq();
+ synchronize_irq(dev->irq);
}
disable_parport_interrupts (dev);
netif_stop_queue (dev);
@@ -840,7 +840,7 @@ plip_send_packet(struct net_device *dev, struct net_local *nl,
if (c0 & 0x08) {
spin_unlock_irq(&nl->lock);
DISABLE(dev->irq);
- synchronize_irq();
+ synchronize_irq(dev->irq);
if (nl->connection == PLIP_CN_RECEIVE) {
/* Interrupted.
We don't need to enable irq,
@@ -1178,7 +1178,7 @@ plip_close(struct net_device *dev)
netif_stop_queue (dev);
DISABLE(dev->irq);
- synchronize_irq();
+ synchronize_irq(dev->irq);
if (dev->irq == -1)
{
diff --git a/drivers/net/tulip/de2104x.c b/drivers/net/tulip/de2104x.c
index 80dcf338487b..fe9796509be8 100644
--- a/drivers/net/tulip/de2104x.c
+++ b/drivers/net/tulip/de2104x.c
@@ -1455,7 +1455,7 @@ static void de_tx_timeout (struct net_device *dev)
/* Update the error counts. */
__de_get_stats(de);
- synchronize_irq();
+ synchronize_irq(dev->irq);
de_clean_rings(de);
de_init_hw(de);
diff --git a/drivers/scsi/qlogicisp.c b/drivers/scsi/qlogicisp.c
index 4d233ac5d9b0..446c1c9308f7 100644
--- a/drivers/scsi/qlogicisp.c
+++ b/drivers/scsi/qlogicisp.c
@@ -84,14 +84,11 @@ struct {
{ \
unsigned long flags; \
\
- save_flags(flags); \
- cli(); \
trace.buf[trace.next].name = (w); \
trace.buf[trace.next].time = jiffies; \
trace.buf[trace.next].index = (i); \
trace.buf[trace.next].addr = (long) (a); \
trace.next = (trace.next + 1) & (TRACE_BUF_LEN - 1); \
- restore_flags(flags); \
}
#else
@@ -1704,9 +1701,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
ENTER("isp1020_load_parameters");
- save_flags(flags);
- cli();
-
hwrev = isp_inw(host, ISP_CFG0) & ISP_CFG0_HWMSK;
isp_cfg1 = ISP_CFG1_F64 | ISP_CFG1_BENAB;
if (hwrev == ISP_CFG0_1040A) {
@@ -1724,7 +1718,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set initiator id failure\n");
return 1;
}
@@ -1736,7 +1729,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set retry count failure\n");
return 1;
}
@@ -1747,7 +1739,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : async data setup time failure\n");
return 1;
}
@@ -1759,7 +1750,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set active negation state failure\n");
return 1;
}
@@ -1771,7 +1761,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set pci control parameter failure\n");
return 1;
}
@@ -1782,7 +1771,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set tag age limit failure\n");
return 1;
}
@@ -1793,7 +1781,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set selection timeout failure\n");
return 1;
}
@@ -1812,7 +1799,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set target parameter failure\n");
return 1;
}
@@ -1827,7 +1813,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set device queue "
"parameter failure\n");
return 1;
@@ -1854,7 +1839,6 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set response queue failure\n");
return 1;
}
@@ -1879,13 +1863,10 @@ static int isp1020_load_parameters(struct Scsi_Host *host)
isp1020_mbox_command(host, param);
if (param[0] != MBOX_COMMAND_COMPLETE) {
- restore_flags(flags);
printk("qlogicisp : set request queue failure\n");
return 1;
}
- restore_flags(flags);
-
LEAVE("isp1020_load_parameters");
return 0;
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 3870d26066e9..09e6b86ee763 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -44,6 +44,16 @@ enum {
#include <asm/hardirq.h>
#include <asm/softirq.h>
+/*
+ * Temporary defines for UP kernels, until all code gets fixed.
+ */
+#if !CONFIG_SMP
+# define cli() local_irq_disable()
+# define sti() local_irq_enable()
+# define save_flags(x) local_irq_save(x)
+# define restore_flags(x) local_irq_restore(x)
+# define save_and_cli(x) local_irq_save_off(x)
+#endif
/* PLEASE, avoid to allocate new softirqs, if you need not _really_ high
diff --git a/include/linux/smp.h b/include/linux/smp.h
index 6e89d1d34bd8..fff7c165ac2d 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -95,7 +95,8 @@ static inline void smp_send_reschedule_all(void) { }
#endif /* !SMP */
-#define get_cpu() ({ preempt_disable(); smp_processor_id(); })
-#define put_cpu() preempt_enable()
+#define get_cpu() ({ preempt_disable(); smp_processor_id(); })
+#define put_cpu() preempt_enable()
+#define put_cpu_no_resched() preempt_enable_no_resched()
#endif /* __LINUX_SMP_H */
--
2.30.9