Changeset d9cf9d5f in mainline

Timestamp:

2006-05-13T12:38:06Z (19 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

e459f12

Parents:

9f581365

Message:

Do not report possible deadlock on fb_lock.
This issue was causing troubles in connection
with slow framebuffer in simulated environment
when false positives triggered an infinite
recursion of attempts to report deadlock on
fb_lock using printf() and fb_putchar().

Files:

• arch/ia32/src/drivers/vesa.c (modified) (1 diff)
• genarch/include/fb/fb.h (modified) (1 diff)
• generic/src/synch/spinlock.c (modified) (2 diffs)

arch/ia32/src/drivers/vesa.c

@@ -75 +75 @@
         /* Map videoram */
         for (a = 0; a < ((vesa_scanline * vesa_height + PAGE_SIZE - 1) >> PAGE_WIDTH); a++)
-                page_mapping_insert(AS_KERNEL, vram_lin_addr+a*4096, vesa_ph_addr+a*4096, PAGE_NOT_CACHEABLE);
+                page_mapping_insert(AS_KERNEL, vram_lin_addr + a*PAGE_SIZE, vesa_ph_addr + a*FRAME_SIZE,
+                        PAGE_NOT_CACHEABLE);
 
         fb_init(vram_lin_addr, vesa_width, vesa_height, vesa_bpp, vesa_scanline);

genarch/include/fb/fb.h

@@ -33 +33 @@
 #include <arch/types.h>
 
+extern spinlock_t fb_lock;
 void fb_init(__address addr, unsigned int x, unsigned int y, unsigned int bpp, unsigned int scan);
 

generic/src/synch/spinlock.c

@@ -41 +41 @@
 #include <symtab.h>
 
+#ifdef CONFIG_FB
+#include <genarch/fb/fb.h>
+#endif
+
 #ifdef CONFIG_SMP
 
@@ -74 +78 @@
         preemption_disable();
         while (test_and_set(&sl->val)) {
-                if (i++ > 300000 && sl!=&printflock) {
+
+                /*
+                 * We need to be careful about printflock and fb_lock.
+                 * Both of them are used to report deadlocks via
+                 * printf() and fb_putchar().
+                 *
+                 * We trust our code that there is no possible deadlock
+                 * caused by these two locks (except when an exception
+                 * is triggered for instance by printf() or fb_putchar()).
+                 * However, we encountered false positives caused by very
+                 * slow VESA framebuffer interaction (especially when
+                 * run in a simulator) that caused problems with both
+                 * printflock and fb_lock.
+                 *
+                 * Possible deadlocks on both printflock and fb_lock
+                 * are therefore not reported as they would cause an
+                 * infinite recursion.
+                 */
+                if (sl == &printflock)
+                        continue;
+#ifdef CONFIG_FB
+                if (sl == &fb_lock)
+                        continue;
+#endif
+                if (i++ > 300000) {
                         printf("cpu%d: looping on spinlock %.*p:%s, caller=%.*p",
                                CPU->id, sizeof(__address) * 2, sl, sl->name, sizeof(__address) * 2, CALLER);