Prevent allocation of buffers if exceeding available memory

[lttng-modules.git] / lib / ringbuffer / ring_buffer_backend.c

diff --git a/lib/ringbuffer/ring_buffer_backend.c b/lib/ringbuffer/ring_buffer_backend.c
index 54c62a996764ee2ee004ee96f3a188801ae6d871..8207f764377a34f5cb0fda0e41da8e56985dbd45 100644 (file)
--- a/lib/ringbuffer/ring_buffer_backend.c
+++ b/lib/ringbuffer/ring_buffer_backend.c
@@ -12,6 +12,7 @@
 #include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
+#include <linux/oom.h>
 #include <linux/cpu.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
@@ -43,6 +44,23 @@ int lib_ring_buffer_backend_allocate(const struct lib_ring_buffer_config *config
        unsigned long i;
 
        num_pages = size >> PAGE_SHIFT;
+
+       /*
+        * Verify that the number of pages requested for that buffer is smaller
+        * than the number of available pages on the system. si_mem_available()
+        * returns an _estimate_ of the number of available pages.
+        */
+       if (num_pages > si_mem_available())
+               goto not_enough_pages;
+
+       /*
+        * Set the current user thread as the first target of the OOM killer.
+        * If the estimate received by si_mem_available() was off, and we do
+        * end up running out of memory because of this buffer allocation, we
+        * want to kill the offending app first.
+        */
+       set_current_oom_origin();
+
        num_pages_per_subbuf = num_pages >> get_count_order(num_subbuf);
        subbuf_size = chanb->subbuf_size;
        num_subbuf_alloc = num_subbuf;
@@ -137,6 +155,7 @@ int lib_ring_buffer_backend_allocate(const struct lib_ring_buffer_config *config
         * will not fault.
         */
        wrapper_vmalloc_sync_all();
+       clear_current_oom_origin();
        vfree(pages);
        return 0;
 
@@ -153,6 +172,8 @@ depopulate:
 array_error:
        vfree(pages);
 pages_error:
+       clear_current_oom_origin();
+not_enough_pages:
        return -ENOMEM;
 }
 
@@ -455,9 +476,11 @@ int channel_backend_init(struct channel_backend *chanb,
 free_bufs:
        if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
-               ret = cpuhp_state_remove_instance(lttng_rb_hp_prepare,
-                               &chanb->cpuhp_prepare.node);
-               WARN_ON(ret);
+               /*
+                * Teardown of lttng_rb_hp_prepare instance
+                * on "add" error is handled within cpu hotplug,
+                * no teardown to do from the caller.
+                */
 #else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
 #ifdef CONFIG_HOTPLUG_CPU
                put_online_cpus();