[IA64] another perfmon fix (take2)

- pfm_context_load(): change return value from EINVAL to EBUSY
  when context is already loaded.

- pfm_check_task_state(): pass test if context state is MASKED.
  It is safe to give access on PFM_CTX_MASKED because the PMU
  state (PMD) is stable and saved in software state.
  This helps multiplexing programs such as the example given
  in libpfm-3.1.

Signed-off-by: stephane eranian <eranian@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 20 insertions, 10 deletions

diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index fd4f3be6e856..71c101601e3e 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -4215,7 +4215,7 @@ pfm_context_load(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
                 DPRINT(("cannot load to [%d], invalid ctx_state=%d\n",
                         req->load_pid,
                         ctx->ctx_state));
-                return -EINVAL;
+                return -EBUSY;
         }
 
         DPRINT(("load_pid [%d] using_dbreg=%d\n", req->load_pid, ctx->ctx_fl_using_dbreg));
@@ -4717,16 +4717,26 @@ recheck:
         if (task == current || ctx->ctx_fl_system) return 0;
 
         /*
-         * if context is UNLOADED we are safe to go
-         */
-        if (state == PFM_CTX_UNLOADED) return 0;
-
-        /*
-         * no command can operate on a zombie context
+         * we are monitoring another thread
          */
-        if (state == PFM_CTX_ZOMBIE) {
-                DPRINT(("cmd %d state zombie cannot operate on context\n", cmd));
-                return -EINVAL;
+        switch(state) {
+                case PFM_CTX_UNLOADED:
+                        /*
+                         * if context is UNLOADED we are safe to go
+                         */
+                        return 0;
+                case PFM_CTX_ZOMBIE:
+                        /*
+                         * no command can operate on a zombie context
+                         */
+                        DPRINT(("cmd %d state zombie cannot operate on context\n", cmd));
+                        return -EINVAL;
+                case PFM_CTX_MASKED:
+                        /*
+                         * PMU state has been saved to software even though
+                         * the thread may still be running.
+                         */
+                        if (cmd != PFM_UNLOAD_CONTEXT) return 0;
         }
 
         /*