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authorIngo Molnar <mingo@elte.hu>2005-06-21 17:14:34 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-21 18:46:13 -0700
commit39c715b71740c4a78ba4769fb54826929bac03cb (patch)
tree94dd679dfc8e6c2db65971739aa8c8c6206f8174 /lib/smp_processor_id.c
parent84929801e14d968caeb84795bfbb88f04283fbd9 (diff)
downloadlinux-39c715b71740c4a78ba4769fb54826929bac03cb.tar.gz
[PATCH] smp_processor_id() cleanup
This patch implements a number of smp_processor_id() cleanup ideas that Arjan van de Ven and I came up with. The previous __smp_processor_id/_smp_processor_id/smp_processor_id API spaghetti was hard to follow both on the implementational and on the usage side. Some of the complexity arose from picking wrong names, some of the complexity comes from the fact that not all architectures defined __smp_processor_id. In the new code, there are two externally visible symbols: - smp_processor_id(): debug variant. - raw_smp_processor_id(): nondebug variant. Replaces all existing uses of _smp_processor_id() and __smp_processor_id(). Defined by every SMP architecture in include/asm-*/smp.h. There is one new internal symbol, dependent on DEBUG_PREEMPT: - debug_smp_processor_id(): internal debug variant, mapped to smp_processor_id(). Also, i moved debug_smp_processor_id() from lib/kernel_lock.c into a new lib/smp_processor_id.c file. All related comments got updated and/or clarified. I have build/boot tested the following 8 .config combinations on x86: {SMP,UP} x {PREEMPT,!PREEMPT} x {DEBUG_PREEMPT,!DEBUG_PREEMPT} I have also build/boot tested x64 on UP/PREEMPT/DEBUG_PREEMPT. (Other architectures are untested, but should work just fine.) Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'lib/smp_processor_id.c')
-rw-r--r--lib/smp_processor_id.c55
1 files changed, 55 insertions, 0 deletions
diff --git a/lib/smp_processor_id.c b/lib/smp_processor_id.c
new file mode 100644
index 000000000000..42c08ef828c5
--- /dev/null
+++ b/lib/smp_processor_id.c
@@ -0,0 +1,55 @@
+/*
+ * lib/smp_processor_id.c
+ *
+ * DEBUG_PREEMPT variant of smp_processor_id().
+ */
+#include <linux/module.h>
+#include <linux/kallsyms.h>
+
+unsigned int debug_smp_processor_id(void)
+{
+ unsigned long preempt_count = preempt_count();
+ int this_cpu = raw_smp_processor_id();
+ cpumask_t this_mask;
+
+ if (likely(preempt_count))
+ goto out;
+
+ if (irqs_disabled())
+ goto out;
+
+ /*
+ * Kernel threads bound to a single CPU can safely use
+ * smp_processor_id():
+ */
+ this_mask = cpumask_of_cpu(this_cpu);
+
+ if (cpus_equal(current->cpus_allowed, this_mask))
+ goto out;
+
+ /*
+ * It is valid to assume CPU-locality during early bootup:
+ */
+ if (system_state != SYSTEM_RUNNING)
+ goto out;
+
+ /*
+ * Avoid recursion:
+ */
+ preempt_disable();
+
+ if (!printk_ratelimit())
+ goto out_enable;
+
+ printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] code: %s/%d\n", preempt_count(), current->comm, current->pid);
+ print_symbol("caller is %s\n", (long)__builtin_return_address(0));
+ dump_stack();
+
+out_enable:
+ preempt_enable_no_resched();
+out:
+ return this_cpu;
+}
+
+EXPORT_SYMBOL(debug_smp_processor_id);
+