Fix battery_bench bug by using a static buffer for stack

Since battery_bench is a TSR (terminate & stay resident) plugin it
cannot allocate the plugin buffer -- various parts of the Rockbox
core make use of it as temporary storage space. The buffer was used
for stack space so this generated false 'Stkov' panics when one of
those in-core users overwrote the buffer.

The default stack size of 1kb is a bit small, so use 4x the default
size to be on the safe side.

This also fixes a minor issue where trying to view OS stack usage
while battery_bench was running would cause audio dropouts, due to
scanning the possibly huge stack with IRQs disabled.

Change-Id: I2e6b76f9946db9090c1af61f7aa0a0dac0698c20

1 files changed, 4 insertions, 21 deletions

diff --git a/apps/plugins/battery_bench.c b/apps/plugins/battery_bench.c
index 6c477cbd09..53931d1930 100644
--- a/apps/plugins/battery_bench.c
+++ b/apps/plugins/battery_bench.c
@@ -30,7 +30,7 @@
 #define EV_EXIT 1337
 
 /* seems to work with 1300, but who knows... */
-#define MIN_THREAD_STACK_SIZE DEFAULT_STACK_SIZE + 0x200
+#define THREAD_STACK_SIZE 4*DEFAULT_STACK_SIZE
 
 #if (CONFIG_KEYPAD == IRIVER_H100_PAD) || \
       (CONFIG_KEYPAD == IRIVER_H300_PAD)
@@ -279,8 +279,7 @@ static struct batt_info
 static struct
 {
     unsigned int id; /* worker thread id */
-    long   *stack;
-    ssize_t stacksize;
+    long stack[THREAD_STACK_SIZE / sizeof(long)];
 } gThread;
 
 static struct event_queue thread_q SHAREDBSS_ATTR;
@@ -607,25 +606,9 @@ enum plugin_status plugin_start(const void* parameter)
     }
 
     rb->memset(&gThread, 0, sizeof(gThread));
-    void   *buf;
-    size_t  buf_size;
-    buf = rb->plugin_get_buffer(&buf_size);
-    ALIGN_BUFFER(buf, buf_size, sizeof(long));
-    rb->memset(buf, 0, buf_size);
-
-    gThread.stacksize = buf_size;
-    gThread.stack = (long *) buf;
-
-    if (gThread.stacksize < MIN_THREAD_STACK_SIZE)
-    {
-        rb->splash(HZ*2, "Out of memory");
-        gThread.id = UINT_MAX;
-        return PLUGIN_ERROR;
-    }
-
     rb->queue_init(&thread_q, true); /* put the thread's queue in the bcast list */
-    gThread.id = rb->create_thread(thread, gThread.stack,
-                                   gThread.stacksize, 0, "Battery Benchmark"
+    gThread.id = rb->create_thread(thread, gThread.stack, sizeof(gThread.stack),
+                                   0, "Battery Benchmark"
                                    IF_PRIO(, PRIORITY_BACKGROUND)
                                    IF_COP(, CPU));