Andrey Ryabinin wrote:
> It's safe to call vfree() from rcu callback as in any other interrupt context.
> Commits you listed bellow didn't change anything in that respect.
> They made impossible to call vfree() under stuff like preempt_disable()/spin_lock()
I still cannot catch. According to test results shown below, calling vfree() from
RCU callback is permitted but calling vfree() from RCU read section is no longer
permitted.
---------- test.c ----------
#include <linux/module.h>
static int test_init(void)
{
rcu_read_lock();
might_sleep();
rcu_read_unlock();
return -EINVAL;
}
module_init(test_init);
MODULE_LICENSE("GPL");
---------- test.c ----------
[ 49.729561] test: loading out-of-tree module taints kernel.
[ 49.738211] test: module verification failed: signature and/or required key missing - tainting kernel
[ 49.757855] ===============================
[ 49.764038] [ ERR: suspicious RCU usage. ]
[ 49.767222] 4.11.0-rc4+ #210 Tainted: G OE
[ 49.770216] -------------------------------
[ 49.772668] ./include/linux/rcupdate.h:521 Illegal context switch in RCU read-side critical section!
[ 49.777915]
other info that might help us debug this:
[ 49.782562]
rcu_scheduler_active = 2, debug_locks = 0
[ 49.786336] 1 lock held by insmod/2332:
[ 49.788596] #0: (rcu_read_lock){......}, at: [<ffffffffc07c7005>] test_init+0x5/0x1000 [test]
[ 49.793632]
stack backtrace:
[ 49.796190] CPU: 2 PID: 2332 Comm: insmod Tainted: G OE 4.11.0-rc4+ #210
[ 49.798830] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013
[ 49.802213] Call Trace:
[ 49.803010] dump_stack+0x85/0xc9
[ 49.804079] lockdep_rcu_suspicious+0xe7/0x120
[ 49.805503] ___might_sleep+0xac/0x250
[ 49.806704] __might_sleep+0x4a/0x90
[ 49.807852] ? 0xffffffffc07c7000
[ 49.808921] test_init+0x5c/0x1000 [test]
[ 49.810212] ? test_init+0x5/0x1000 [test]
[ 49.811526] do_one_initcall+0x51/0x1c0
[ 49.813014] ? do_init_module+0x27/0x1fc
[ 49.814370] ? rcu_read_lock_sched_held+0x98/0xa0
[ 49.815882] ? kmem_cache_alloc_trace+0x278/0x2e0
[ 49.817389] ? do_init_module+0x27/0x1fc
[ 49.818651] do_init_module+0x60/0x1fc
[ 49.819880] load_module+0x23b4/0x2a00
[ 49.821087] ? __symbol_put+0x70/0x70
[ 49.822271] ? vfs_read+0x12b/0x180
[ 49.823401] SYSC_finit_module+0xa6/0xf0
[ 49.824667] SyS_finit_module+0xe/0x10
[ 49.825894] do_syscall_64+0x6c/0x200
[ 49.827074] entry_SYSCALL64_slow_path+0x25/0x25
[ 49.829239] RIP: 0033:0x7fdeb1f52bf9
[ 49.830540] RSP: 002b:00007fff1f355b28 EFLAGS: 00000206 ORIG_RAX: 0000000000000139
[ 49.833255] RAX: ffffffffffffffda RBX: 00000000014e71f0 RCX: 00007fdeb1f52bf9
[ 49.835586] RDX: 0000000000000000 RSI: 000000000041a2d8 RDI: 0000000000000003
[ 49.838370] RBP: 000000000041a2d8 R08: 0000000000000000 R09: 00007fff1f355cc8
[ 49.841099] R10: 0000000000000003 R11: 0000000000000206 R12: 0000000000000000
[ 49.843994] R13: 00000000014e6130 R14: 0000000000000000 R15: 0000000000000000
[ 49.846756] BUG: sleeping function called from invalid context at /data/linux/akari/test.c:5
[ 49.850727] in_atomic(): 1, irqs_disabled(): 0, pid: 2332, name: insmod
[ 49.853353] INFO: lockdep is turned off.
[ 49.855088] CPU: 2 PID: 2332 Comm: insmod Tainted: G OE 4.11.0-rc4+ #210
[ 49.858013] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013
[ 49.861940] Call Trace:
[ 49.863217] dump_stack+0x85/0xc9
[ 49.864744] ___might_sleep+0x184/0x250
[ 49.866420] __might_sleep+0x4a/0x90
[ 49.868003] ? 0xffffffffc07c7000
[ 49.869502] test_init+0x5c/0x1000 [test]
[ 49.871236] ? test_init+0x5/0x1000 [test]
[ 49.872983] do_one_initcall+0x51/0x1c0
[ 49.874796] ? do_init_module+0x27/0x1fc
[ 49.876486] ? rcu_read_lock_sched_held+0x98/0xa0
[ 49.878413] ? kmem_cache_alloc_trace+0x278/0x2e0
[ 49.880330] ? do_init_module+0x27/0x1fc
[ 49.882006] do_init_module+0x60/0x1fc
[ 49.883623] load_module+0x23b4/0x2a00
[ 49.885225] ? __symbol_put+0x70/0x70
[ 49.886784] ? vfs_read+0x12b/0x180
[ 49.888291] SYSC_finit_module+0xa6/0xf0
[ 49.890025] SyS_finit_module+0xe/0x10
[ 49.891611] do_syscall_64+0x6c/0x200
[ 49.893168] entry_SYSCALL64_slow_path+0x25/0x25
[ 49.895027] RIP: 0033:0x7fdeb1f52bf9
[ 49.896561] RSP: 002b:00007fff1f355b28 EFLAGS: 00000206 ORIG_RAX: 0000000000000139
[ 49.899355] RAX: ffffffffffffffda RBX: 00000000014e71f0 RCX: 00007fdeb1f52bf9
[ 49.902020] RDX: 0000000000000000 RSI: 000000000041a2d8 RDI: 0000000000000003
[ 49.904683] RBP: 000000000041a2d8 R08: 0000000000000000 R09: 00007fff1f355cc8
[ 49.907510] R10: 0000000000000003 R11: 0000000000000206 R12: 0000000000000000
[ 49.910180] R13: 00000000014e6130 R14: 0000000000000000 R15: 0000000000000000
---------- test.c ----------
#include <linux/module.h>
#include <linux/sched.h>
static int test_init(void)
{
static DEFINE_SPINLOCK(lock);
rcu_read_lock();
spin_lock(&lock);
cond_resched_lock(&lock);
spin_unlock(&lock);
rcu_read_unlock();
return -EINVAL;
}
module_init(test_init);
MODULE_LICENSE("GPL");
---------- test.c ----------
[ 66.548461] test: loading out-of-tree module taints kernel.
[ 66.551894] test: module verification failed: signature and/or required key missing - tainting kernel
[ 66.560299] ===============================
[ 66.562838] [ ERR: suspicious RCU usage. ]
[ 66.565395] 4.11.0-rc4+ #210 Tainted: G OE
[ 66.568494] -------------------------------
[ 66.571012] ./include/linux/rcupdate.h:521 Illegal context switch in RCU read-side critical section!
[ 66.576384]
other info that might help us debug this:
[ 66.579234]
rcu_scheduler_active = 2, debug_locks = 0
[ 66.581505] 2 locks held by insmod/2336:
[ 66.582897] #0: (rcu_read_lock){......}, at: [<ffffffffc0543005>] test_init+0x5/0x1000 [test]
[ 66.586253] #1: (lock#4){+.+...}, at: [<ffffffffc0543055>] test_init+0x55/0x1000 [test]
[ 66.589135]
stack backtrace:
[ 66.590919] CPU: 0 PID: 2336 Comm: insmod Tainted: G OE 4.11.0-rc4+ #210
[ 66.593842] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013
[ 66.597716] Call Trace:
[ 66.598598] dump_stack+0x85/0xc9
[ 66.599749] lockdep_rcu_suspicious+0xe7/0x120
[ 66.601289] ___might_sleep+0xac/0x250
[ 66.602585] ? 0xffffffffc0543000
[ 66.603735] test_init+0x6b/0x1000 [test]
[ 66.605121] ? test_init+0x5/0x1000 [test]
[ 66.606520] do_one_initcall+0x51/0x1c0
[ 66.607850] ? do_init_module+0x27/0x1fc
[ 66.609245] ? rcu_read_lock_sched_held+0x98/0xa0
[ 66.610855] ? kmem_cache_alloc_trace+0x278/0x2e0
[ 66.612489] ? do_init_module+0x27/0x1fc
[ 66.613868] do_init_module+0x60/0x1fc
[ 66.615195] load_module+0x23b4/0x2a00
[ 66.616512] ? __symbol_put+0x70/0x70
[ 66.617816] ? vfs_read+0x12b/0x180
[ 66.619074] SYSC_finit_module+0xa6/0xf0
[ 66.620455] SyS_finit_module+0xe/0x10
[ 66.621780] do_syscall_64+0x6c/0x200
[ 66.623067] entry_SYSCALL64_slow_path+0x25/0x25
[ 66.624937] RIP: 0033:0x7f6e6702bbf9
[ 66.626206] RSP: 002b:00007ffdc94c3588 EFLAGS: 00000206 ORIG_RAX: 0000000000000139
[ 66.628901] RAX: ffffffffffffffda RBX: 00000000007421f0 RCX: 00007f6e6702bbf9
[ 66.631373] RDX: 0000000000000000 RSI: 000000000041a2d8 RDI: 0000000000000003
[ 66.634430] RBP: 000000000041a2d8 R08: 0000000000000000 R09: 00007ffdc94c3728
[ 66.637428] R10: 0000000000000003 R11: 0000000000000206 R12: 0000000000000000
[ 66.640422] R13: 0000000000741130 R14: 0000000000000000 R15: 0000000000000000
[ 66.643430] BUG: sleeping function called from invalid context at /data/linux/akari/test.c:8
[ 66.646779] in_atomic(): 1, irqs_disabled(): 0, pid: 2336, name: insmod
[ 66.649484] INFO: lockdep is turned off.
[ 66.651284] CPU: 0 PID: 2336 Comm: insmod Tainted: G OE 4.11.0-rc4+ #210
[ 66.654377] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013
[ 66.658592] Call Trace:
[ 66.659939] dump_stack+0x85/0xc9
[ 66.661562] ___might_sleep+0x184/0x250
[ 66.663385] ? 0xffffffffc0543000
[ 66.664967] test_init+0x6b/0x1000 [test]
[ 66.666812] ? test_init+0x5/0x1000 [test]
[ 66.668636] do_one_initcall+0x51/0x1c0
[ 66.670399] ? do_init_module+0x27/0x1fc
[ 66.672170] ? rcu_read_lock_sched_held+0x98/0xa0
[ 66.674256] ? kmem_cache_alloc_trace+0x278/0x2e0
[ 66.676308] ? do_init_module+0x27/0x1fc
[ 66.678056] do_init_module+0x60/0x1fc
[ 66.679728] load_module+0x23b4/0x2a00
[ 66.681428] ? __symbol_put+0x70/0x70
[ 66.683100] ? vfs_read+0x12b/0x180
[ 66.684720] SYSC_finit_module+0xa6/0xf0
[ 66.686422] SyS_finit_module+0xe/0x10
[ 66.688109] do_syscall_64+0x6c/0x200
[ 66.689776] entry_SYSCALL64_slow_path+0x25/0x25
[ 66.692052] RIP: 0033:0x7f6e6702bbf9
[ 66.693687] RSP: 002b:00007ffdc94c3588 EFLAGS: 00000206 ORIG_RAX: 0000000000000139
[ 66.696577] RAX: ffffffffffffffda RBX: 00000000007421f0 RCX: 00007f6e6702bbf9
[ 66.699432] RDX: 0000000000000000 RSI: 000000000041a2d8 RDI: 0000000000000003
[ 66.702261] RBP: 000000000041a2d8 R08: 0000000000000000 R09: 00007ffdc94c3728
[ 66.705076] R10: 0000000000000003 R11: 0000000000000206 R12: 0000000000000000
[ 66.707990] R13: 0000000000741130 R14: 0000000000000000 R15: 0000000000000000
Also, if we try below change like suggested at
http://lkml.kernel.org/r/20170323152949.GA29134@xxxxxxxxxxxxxxxxxxxxxx ,
we get below warnings.
Aren't there vfree()/kvfree() users who are not ready to handle these changes?
----------
diff --git a/mm/util.c b/mm/util.c
index 656dc5e..2a2ef72 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -331,6 +331,12 @@ unsigned long vm_mmap(struct file *file, unsigned long addr,
void kvfree(const void *addr)
{
+ /* Detect errors before kvmalloc() falls back to vmalloc(). */
+ if (addr) {
+ WARN_ON(in_nmi());
+ if (likely(!in_interrupt()))
+ might_sleep();
+ }
if (is_vmalloc_addr(addr))
vfree(addr);
else
----------
[ 23.635540] BUG: sleeping function called from invalid context at mm/util.c:338
[ 23.638701] in_atomic(): 1, irqs_disabled(): 0, pid: 478, name: kworker/0:1H
[ 23.641516] 3 locks held by kworker/0:1H/478:
[ 23.643476] #0: ("xfs-log/%s"mp->m_fsname){.+.+..}, at: [<ffffffffb20d1e64>] process_one_work+0x194/0x6c0
[ 23.647176] #1: ((&bp->b_ioend_work)){+.+...}, at: [<ffffffffb20d1e64>] process_one_work+0x194/0x6c0
[ 23.650939] #2: (&(&pag->pagb_lock)->rlock){+.+...}, at: [<ffffffffc02b42ee>] xfs_extent_busy_clear+0x9e/0xe0 [xfs]
[ 23.655132] CPU: 0 PID: 478 Comm: kworker/0:1H Not tainted 4.11.0-rc4+ #212
[ 23.657974] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013
[ 23.662041] Workqueue: xfs-log/sda1 xfs_buf_ioend_work [xfs]
[ 23.664463] Call Trace:
[ 23.665866] dump_stack+0x85/0xc9
[ 23.667538] ___might_sleep+0x184/0x250
[ 23.669371] __might_sleep+0x4a/0x90
[ 23.671137] kvfree+0x41/0x90
[ 23.672748] xfs_extent_busy_clear_one+0x51/0x190 [xfs]
[ 23.675110] xfs_extent_busy_clear+0xbb/0xe0 [xfs]
[ 23.677278] xlog_cil_committed+0x241/0x420 [xfs]
[ 23.679431] xlog_state_do_callback+0x170/0x2d0 [xfs]
[ 23.681717] xlog_state_done_syncing+0x7f/0xa0 [xfs]
[ 23.683971] ? xfs_buf_ioend_work+0x15/0x20 [xfs]
[ 23.686112] xlog_iodone+0x86/0xc0 [xfs]
[ 23.688007] xfs_buf_ioend+0xd3/0x440 [xfs]
[ 23.689999] xfs_buf_ioend_work+0x15/0x20 [xfs]
[ 23.692060] process_one_work+0x21c/0x6c0
[ 23.694177] ? process_one_work+0x194/0x6c0
[ 23.696120] worker_thread+0x137/0x4b0
[ 23.697973] kthread+0x10f/0x150
[ 23.699607] ? process_one_work+0x6c0/0x6c0
[ 23.701561] ? kthread_create_on_node+0x70/0x70
[ 23.703617] ret_from_fork+0x31/0x40
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