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authorAnton Blanchard <anton@samba.org>2010-03-05 16:42:55 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2010-03-06 14:26:33 -0500
commit8aeee85a29e27e043db582bf2ae8e5f42767934f (patch)
treefac5fc9b79dc272517918722e944b86f36a7e608
parent78d7d407b62a021e6d2e8dc24c0b90e390ab58a1 (diff)
panic: fix panic_timeout accuracy when running on a hypervisor
I've had some complaints about panic_timeout being wildly innacurate on shared processor PowerPC partitions (a 3 minute panic_timeout taking 30 minutes). The problem is we loop on mdelay(1) and with a 1ms in 10ms hypervisor timeslice each of these will take 10ms (ie 10x) longer. I expect other platforms with shared processor hypervisors will see the same issue. This patch keeps the old behaviour if we have a panic_blink (only keyboard LEDs right now) and does 1 second mdelays if we don't. Signed-off-by: Anton Blanchard <anton@samba.org> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/panic.c46
1 files changed, 30 insertions, 16 deletions
diff --git a/kernel/panic.c b/kernel/panic.c
index c787333282b8..13d966b4c14a 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -36,15 +36,36 @@ ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
36 36
37EXPORT_SYMBOL(panic_notifier_list); 37EXPORT_SYMBOL(panic_notifier_list);
38 38
39static long no_blink(long time)
40{
41 return 0;
42}
43
44/* Returns how long it waited in ms */ 39/* Returns how long it waited in ms */
45long (*panic_blink)(long time); 40long (*panic_blink)(long time);
46EXPORT_SYMBOL(panic_blink); 41EXPORT_SYMBOL(panic_blink);
47 42
43static void panic_blink_one_second(void)
44{
45 static long i = 0, end;
46
47 if (panic_blink) {
48 end = i + MSEC_PER_SEC;
49
50 while (i < end) {
51 i += panic_blink(i);
52 mdelay(1);
53 i++;
54 }
55 } else {
56 /*
57 * When running under a hypervisor a small mdelay may get
58 * rounded up to the hypervisor timeslice. For example, with
59 * a 1ms in 10ms hypervisor timeslice we might inflate a
60 * mdelay(1) loop by 10x.
61 *
62 * If we have nothing to blink, spin on 1 second calls to
63 * mdelay to avoid this.
64 */
65 mdelay(MSEC_PER_SEC);
66 }
67}
68
48/** 69/**
49 * panic - halt the system 70 * panic - halt the system
50 * @fmt: The text string to print 71 * @fmt: The text string to print
@@ -95,9 +116,6 @@ NORET_TYPE void panic(const char * fmt, ...)
95 116
96 bust_spinlocks(0); 117 bust_spinlocks(0);
97 118
98 if (!panic_blink)
99 panic_blink = no_blink;
100
101 if (panic_timeout > 0) { 119 if (panic_timeout > 0) {
102 /* 120 /*
103 * Delay timeout seconds before rebooting the machine. 121 * Delay timeout seconds before rebooting the machine.
@@ -105,11 +123,9 @@ NORET_TYPE void panic(const char * fmt, ...)
105 */ 123 */
106 printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout); 124 printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
107 125
108 for (i = 0; i < panic_timeout*1000; ) { 126 for (i = 0; i < panic_timeout; i++) {
109 touch_nmi_watchdog(); 127 touch_nmi_watchdog();
110 i += panic_blink(i); 128 panic_blink_one_second();
111 mdelay(1);
112 i++;
113 } 129 }
114 /* 130 /*
115 * This will not be a clean reboot, with everything 131 * This will not be a clean reboot, with everything
@@ -135,11 +151,9 @@ NORET_TYPE void panic(const char * fmt, ...)
135 } 151 }
136#endif 152#endif
137 local_irq_enable(); 153 local_irq_enable();
138 for (i = 0; ; ) { 154 while (1) {
139 touch_softlockup_watchdog(); 155 touch_softlockup_watchdog();
140 i += panic_blink(i); 156 panic_blink_one_second();
141 mdelay(1);
142 i++;
143 } 157 }
144} 158}
145 159