[PATCH] ia64: perfmon stack consumption fix

This patch moves the pfm_ovfl_arg_t structure from the kernel stack
into the pfm_context_t structure. This minimizes kernel stack space
consumption.
Signed-off-by: Stephane Eranian <eranian@hpl.hp.com>
Signed-off-by: David Mosberger <davidm@hpl.hp.com>

arch/ia64/kernel/perfmon.c

@@ -311,6 +311,7 @@ typedef struct pfm_context {
 	unsigned int		ctx_cpu;		/* cpu to which perfmon is applied (system wide) */
 
 	int			ctx_fd;			/* file descriptor used my this context */
+	pfm_ovfl_arg_t		ctx_ovfl_arg;		/* argument to custom buffer format handler */
 
 	pfm_buffer_fmt_t	*ctx_buf_fmt;		/* buffer format callbacks */
 	void			*ctx_smpl_hdr;		/* points to sampling buffer header kernel vaddr */
@@ -5160,7 +5161,7 @@ pfm_end_notify_user(pfm_context_t *ctx)
 static void
 pfm_overflow_handler(struct task_struct *task, pfm_context_t *ctx, u64 pmc0, struct pt_regs *regs)
 {
-	pfm_ovfl_arg_t ovfl_arg;
+	pfm_ovfl_arg_t *ovfl_arg;
 	unsigned long mask;
 	unsigned long old_val, ovfl_val, new_val;
 	unsigned long ovfl_notify = 0UL, ovfl_pmds = 0UL, smpl_pmds = 0UL, reset_pmds;
@@ -5247,7 +5248,8 @@ pfm_overflow_handler(struct task_struct *task, pfm_context_t *ctx, u64 pmc0, str
 		int j, k, ret = 0;
 		int this_cpu = smp_processor_id();
 
-		pmd_mask   = ovfl_pmds >> PMU_FIRST_COUNTER;
+		pmd_mask = ovfl_pmds >> PMU_FIRST_COUNTER;
+		ovfl_arg = &ctx->ctx_ovfl_arg;
 
 		prefetch(ctx->ctx_smpl_hdr);
 
@@ -5257,15 +5259,15 @@ pfm_overflow_handler(struct task_struct *task, pfm_context_t *ctx, u64 pmc0, str
 
 			if ((pmd_mask & 0x1) == 0) continue;
 
-			ovfl_arg.ovfl_pmd      = (unsigned char )i;
-			ovfl_arg.ovfl_notify   = ovfl_notify & mask ? 1 : 0;
-			ovfl_arg.active_set    = 0;
-			ovfl_arg.ovfl_ctrl.val = 0; /* module must fill in all fields */
-			ovfl_arg.smpl_pmds[0]  = smpl_pmds = ctx->ctx_pmds[i].smpl_pmds[0];
+			ovfl_arg->ovfl_pmd      = (unsigned char )i;
+			ovfl_arg->ovfl_notify   = ovfl_notify & mask ? 1 : 0;
+			ovfl_arg->active_set    = 0;
+			ovfl_arg->ovfl_ctrl.val = 0; /* module must fill in all fields */
+			ovfl_arg->smpl_pmds[0]  = smpl_pmds = ctx->ctx_pmds[i].smpl_pmds[0];
 
-			ovfl_arg.pmd_value      = ctx->ctx_pmds[i].val;
-			ovfl_arg.pmd_last_reset = ctx->ctx_pmds[i].lval;
-			ovfl_arg.pmd_eventid    = ctx->ctx_pmds[i].eventid;
+			ovfl_arg->pmd_value      = ctx->ctx_pmds[i].val;
+			ovfl_arg->pmd_last_reset = ctx->ctx_pmds[i].lval;
+			ovfl_arg->pmd_eventid    = ctx->ctx_pmds[i].eventid;
 
 			/*
 		 	 * copy values of pmds of interest. Sampling format may copy them
@@ -5274,8 +5276,8 @@ pfm_overflow_handler(struct task_struct *task, pfm_context_t *ctx, u64 pmc0, str
 			if (smpl_pmds) {
 				for(j=0, k=0; smpl_pmds; j++, smpl_pmds >>=1) {
 					if ((smpl_pmds & 0x1) == 0) continue;
-					ovfl_arg.smpl_pmds_values[k++] = PMD_IS_COUNTING(j) ?  pfm_read_soft_counter(ctx, j) : ia64_get_pmd(j);
-					DPRINT_ovfl(("smpl_pmd[%d]=pmd%u=0x%lx\n", k-1, j, ovfl_arg.smpl_pmds_values[k-1]));
+					ovfl_arg->smpl_pmds_values[k++] = PMD_IS_COUNTING(j) ?  pfm_read_soft_counter(ctx, j) : ia64_get_pmd(j);
+					DPRINT_ovfl(("smpl_pmd[%d]=pmd%u=0x%lx\n", k-1, j, ovfl_arg->smpl_pmds_values[k-1]));
 				}
 			}
 
@@ -5286,7 +5288,7 @@ pfm_overflow_handler(struct task_struct *task, pfm_context_t *ctx, u64 pmc0, str
 			/*
 		 	 * call custom buffer format record (handler) routine
 		 	 */
-			ret = (*ctx->ctx_buf_fmt->fmt_handler)(task, ctx->ctx_smpl_hdr, &ovfl_arg, regs, tstamp);
+			ret = (*ctx->ctx_buf_fmt->fmt_handler)(task, ctx->ctx_smpl_hdr, ovfl_arg, regs, tstamp);
 
 			end_cycles = ia64_get_itc();
 
@@ -5294,13 +5296,13 @@ pfm_overflow_handler(struct task_struct *task, pfm_context_t *ctx, u64 pmc0, str
 			 * For those controls, we take the union because they have
 			 * an all or nothing behavior.
 			 */
-			ovfl_ctrl.bits.notify_user     |= ovfl_arg.ovfl_ctrl.bits.notify_user;
-			ovfl_ctrl.bits.block_task      |= ovfl_arg.ovfl_ctrl.bits.block_task;
-			ovfl_ctrl.bits.mask_monitoring |= ovfl_arg.ovfl_ctrl.bits.mask_monitoring;
+			ovfl_ctrl.bits.notify_user     |= ovfl_arg->ovfl_ctrl.bits.notify_user;
+			ovfl_ctrl.bits.block_task      |= ovfl_arg->ovfl_ctrl.bits.block_task;
+			ovfl_ctrl.bits.mask_monitoring |= ovfl_arg->ovfl_ctrl.bits.mask_monitoring;
 			/*
 			 * build the bitmask of pmds to reset now
 			 */
-			if (ovfl_arg.ovfl_ctrl.bits.reset_ovfl_pmds) reset_pmds |= mask;
+			if (ovfl_arg->ovfl_ctrl.bits.reset_ovfl_pmds) reset_pmds |= mask;
 
 			pfm_stats[this_cpu].pfm_smpl_handler_cycles += end_cycles - start_cycles;
 		}