ia64: fix perfmon bug causing lost samples

	Patch from Stephane: Fix a bug in perfmon_default_smpl.c by
	which we would systematically lose one sample at every buffer
	overflow.

diff --git a/arch/ia64/kernel/perfmon_default_smpl.c b/arch/ia64/kernel/perfmon_default_smpl.c
index 92f58ab8834f32af97de86a3ff377e655c3966d8..38a84cf85f06a72debb7ef53d2c4ac6b3a0aca2d 100644 (file)
--- a/arch/ia64/kernel/perfmon_default_smpl.c
+++ b/arch/ia64/kernel/perfmon_default_smpl.c
@@ -114,7 +114,7 @@ default_handler(struct task_struct *task, void *buf, pfm_ovfl_arg_t *arg, struct
        pfm_default_smpl_hdr_t *hdr;
        pfm_default_smpl_entry_t *ent;
        void *cur, *last;
-       unsigned long *e;
+       unsigned long *e, entry_size;
        unsigned int npmds, i;
        unsigned char ovfl_pmd;
        unsigned char ovfl_notify;
@@ -131,8 +131,7 @@ default_handler(struct task_struct *task, void *buf, pfm_ovfl_arg_t *arg, struct
        ovfl_notify = arg->ovfl_notify;
 
        /*
-        * check for space against largest possibly entry.
-        * We may waste space at the end of the buffer.
+        * precheck for sanity
         */
        if ((last - cur) < PFM_DEFAULT_MAX_ENTRY_SIZE) goto full;
 
@@ -142,6 +141,8 @@ default_handler(struct task_struct *task, void *buf, pfm_ovfl_arg_t *arg, struct
 
        prefetch(arg->smpl_pmds_values);
 
+       entry_size = sizeof(*ent) + (npmds << 3);
+
        /* position for first pmd */
        e = (unsigned long *)(ent+1);
 
@@ -191,7 +192,13 @@ default_handler(struct task_struct *task, void *buf, pfm_ovfl_arg_t *arg, struct
        /*
         * update position for next entry
         */
-       hdr->hdr_cur_offs += sizeof(*ent) + (npmds << 3);
+       hdr->hdr_cur_offs += entry_size;
+       cur               += entry_size;
+
+       /*
+        * post check to avoid losing the last sample
+        */
+       if ((last - cur) < PFM_DEFAULT_MAX_ENTRY_SIZE) goto full;
 
        /*
         * keep same ovfl_pmds, ovfl_notify