On Wed, Feb 3, 2016 at 2:11 PM, Jiri Kosina <[email protected]> wrote: > On Tue, 2 Feb 2016, Dmitry Vyukov wrote: > >> Hello, >> >> If the following program run in a parallel loop, eventually it leaves >> hanged uninterruptable tasks on mmap_sem. >> >> [ 4074.740298] sysrq: SysRq : Show Locks Held >> [ 4074.740780] Showing all locks held in the system: >> ... >> [ 4074.762133] 1 lock held by a.out/1276: >> [ 4074.762427] #0: (&mm->mmap_sem){++++++}, at: [<ffffffff816df89c>] >> __mm_populate+0x25c/0x350 >> [ 4074.763149] 1 lock held by a.out/1147: >> [ 4074.763438] #0: (&mm->mmap_sem){++++++}, at: [<ffffffff816b3bbc>] >> vm_mmap_pgoff+0x12c/0x1b0 >> [ 4074.764164] 1 lock held by a.out/1284: >> [ 4074.764447] #0: (&mm->mmap_sem){++++++}, at: [<ffffffff816df89c>] >> __mm_populate+0x25c/0x350 >> [ 4074.765287] > > I've now tried to reproduce this on 4.5-rc1 (with the lock_fdc() fix > applied), and I am not seeing any stuck tasks so far. > > Could you please provide more details about the reproduction scenario? > Namely, how many parallel invocations are you typically running (and how > many cores does the system in question have), and what is the typical time > that you need for the problem to appear?
Qemu with 4 cores, 32 parallel processes, it took 20 seconds (2409 program executions) to hang 2 of them just now.
